Two condos went up for sale in Boston this year at nearly identical prices. One, a full-service unit at 135 Seaport Boulevard, traded within weeks at a premium price per square foot. The other, a similarly priced unit in the Seaport's ultra-luxury tier, sat through the spring and into summer with no accepted offer. Same neighborhood. Same zip code. Same skyline view, in some cases. Wildly different outcomes.
If you've been comparing Boston neighborhoods by median price per square foot, that gap should give you pause. The number that gets quoted most often when people talk about the Seaport, its position as the priciest square footage in the city, is also the number that hides the most important thing happening inside that market. And the same pattern shows up across town in Back Bay, for a completely different reason.
The number everyone quotes, and what it's averaging over
By most measures, the Seaport carries the highest price per square foot of any Boston submarket, with figures in 2026 ranging from roughly $1,800 to $2,200 depending on the building and the quarter. Back Bay, by comparison, has posted figures closer to $1,450 to $1,627 per square foot over the same period. On paper, that makes the Seaport the more expensive place to buy.
But price per square foot only tells you what happened on average. It doesn't tell you how long it took, or which units inside that average were the ones actually moving.
| Submarket | Price per sq ft (2026) | Median days on market |
|---|---|---|
| Seaport core | ~$1,940 (March 2026) | 93 days (March 2026), improving to 62 days by Q2 2026 |
| Back Bay | ~$1,450 (March 2026) | 44 days (March 2026) |
| South Boston Waterfront | ~$996 (March 2026) | 54 days (March 2026) |
The Seaport's own market held the highest price tag and the slowest pace, even as citywide condo days-on-market for 2026 generally ran in the 32 to 38 day range. That combination, highest price and slowest sale, is not what a simple supply-and-demand story would predict. If a neighborhood commands the biggest premium, it should also be the market clearing fastest. It wasn't.
Two markets wearing one zip code
The explanation sits inside the Seaport itself, not between the Seaport and everywhere else. Established, well-positioned buildings such as 135 Seaport Boulevard and St. Regis Residences have continued to trade with confidence, commanding $1,500 to $2,255 per square foot depending on the unit and floor. Those sales happen briskly because buyers know exactly what they're getting: full-service staffing, harbor views, and a building with a track record.
The drag comes from above. The segment priced over $3 million has been sitting on real oversupply through 2026. St. Regis Residences alone reportedly still carried around 47 unsold units earlier this year, and sales of Boston urban-core properties above $3 million fell an estimated 35 percent year over year in the second quarter. Developers in that tier have leaned on price reductions and closing-cost concessions to move inventory, which tells you the buyer pool at that price point is thinner and pickier than the skyline suggests.
By the second quarter of 2026, Seaport's overall pace had picked up, with average days on market dropping to roughly 62 as inventory grew and closed sales held steady. That's real improvement. But it doesn't erase the underlying split. A mid-market Seaport buyer and a $4 million penthouse buyer are shopping in two different markets that happen to share a mailing address, and the neighborhood-wide median blends them into one number that describes neither one accurately.
The same split shows up in Back Bay, for a different reason
Back Bay's headline numbers look calmer. Inventory there has been described as critically scarce through most of 2026, and that scarcity has kept the overall market moving faster than the Seaport, generally in the 42 to 46 day range, with cash buyers making up an unusually large share of transactions.
But look inside Back Bay's own listings and the same fork in the road appears. Renovated, full-service units, the ones with 24/7 concierge, climate control, and underground parking, have reportedly been commanding upward of $1,900 per square foot and selling in under 30 days. Meanwhile, unrenovated brownstones on the same blocks have been sitting 60 days or longer, even at premium addresses.
Part of that is Back Bay's built environment. Its brownstones sit inside a protected historic district, which means exterior work, from windows to façade repairs, requires review before it can begin. That review process is a real constraint for anyone weighing a renovation, and it changes the calculus for buyers deciding between move-in-ready and a project. A buyer looking at two brownstones with identical square footage and asking price may be looking at two very different timelines to close, and two very different timelines to actually live there.
What the carrying costs add that the price tag doesn't
Price per square foot also leaves out what it costs to own the place month to month, and that gap is wider than most buyers expect.
In the Seaport, full-service buildings function closer to hospitality properties than traditional condo associations. Monthly fees at addresses like St. Regis Residences have run in the range of $1,700 to $3,500, climbing above $5,800 for penthouse-tier units, a cost that reflects concierge staffing, wellness amenities, and reserve funding rather than square footage.
Back Bay's carrying costs come from a different source. Buildings there average over a century old, and monthly fees of $1,200 to $2,500 or more go toward maintaining ornate masonry, slate roofs, copper gutters, and historic elevators, expenses that don't show up until you read the association's reserve study. Parking adds its own layer. Deeded spots in Back Bay have reportedly changed hands for $300,000 to $450,000 on their own, sometimes representing a fifth or more of a condo's total value, while buyers without a deeded spot are looking at monthly garage rentals near the Prudential Center or Boston Common that add up over a decade of ownership.
None of that appears in a headline price-per-square-foot figure. All of it affects what the unit actually costs you to own.
What this means if you're comparing the two
The practical takeaway isn't that one neighborhood beats the other. It's that neighborhood-level averages are the wrong tool for the decision in front of you. Before comparing Seaport to Back Bay, or any specific listing to a citywide number, it helps to ask:
- Is this building's recent sale history closer to the neighborhood's fast-moving segment or its slow-moving one?
- What does the reserve study or HOA minutes from the last three years say about upcoming special assessments?
- Is parking deeded, and if not, what does a monthly rental actually cost over the years you plan to own?
- If the unit needs renovation, does it fall inside a historic district review process, and what does that add to the timeline?
Those questions matter more than which neighborhood's median looks better on a spreadsheet, because the median was never describing your unit in the first place.
A note on timing
Both of these markets moved through 2026 with more inventory than the year before, which gave buyers more room to ask these questions before making an offer. That window doesn't stay open indefinitely. A market with 12.9 months of supply, which Seaport carried for part of 2026, behaves very differently a year later once the oversupplied segment works itself off the books.
FAQ
Is Back Bay a better investment than the Seaport? Neither answer holds up across the board. Back Bay has shown steadier price support due to scarce inventory, while the Seaport has shown faster appreciation in its established buildings alongside real softness in its ultra-luxury tier. The better question is which specific building and unit condition you're evaluating.
Why do some Back Bay brownstones sit on the market for months? Several factors can contribute, including the property's condition, price relative to comparable turnkey units, and the added timeline of exterior renovation review inside the Back Bay Architectural District. Buyers weighing a project should factor that review process into their planning from the start.
Does a higher price per square foot mean a better location? Not necessarily. It often reflects the building's amenity level and service model as much as the address itself. Two buildings a block apart can post very different per-square-foot figures based on whether they offer full-service staffing, parking, and recent renovation.
If you're weighing a purchase or a sale in Boston and want a clearer read on what a specific building or block is actually doing, not just what the neighborhood average suggests, the Louise Touchette Team can walk through the comparable sales and carrying costs that apply to your situation. Request a Complimentary Home Valuation to start with real numbers instead of a citywide average.
