I ask this because just from my observations, it seems like people who aren't Celtics fans consider Boston more of a mid-market team (sort of like the Spurs, Blazers, Hawks, Thunder, etc.), while they think the extreme growth of teams like Miami, LAC, Golden State over the years make them more "Big Market" along with the obvious NY, LAL, CHI.
My pal from Atlanta thinks Boston is a big market team BUT on the lower end of that spectrum (as in there are like 8-9 other "valuable/bigger" teams right now). He thinks the legacy and championships of the past are what keeps Boston big market for now (which is probably/likely true).
I know Forbes back in January 2016 made a list ranking the franchises by value, and Boston came 4th trailing Chicago, NY, and LAL (no surprise there). LA and NY are always a big market because their cities are much larger (than Boston as well), and television market is enormous. When it comes to nationally televised games like those on ABC.. they usually choose NY, LAL, LAC, MIA, GSW, CHI, OKC, etc. before a Boston game, even if LA/NY are having a horrible season. That's probably representative of the market too. (Not that I really care about whether the Celtics game is nationally televised or not..)
I don't know am I overthinking this? I know it doesn't really matter in a sense but I'm just curious. I've always considered Boston Big Market and that's why I assume, like Wyc did in the Big 3 Era, soon he will be willing to pay a HUGE luxury tax to keep key players around and to build a contender.