If there was a glut of this type of housing, then developers would not be able to fill their luxury units or get the prices they wanted. The financiers of such projects would notice this and realize that maybe it's not such a good idea to finance such projects. But this isn't happening, and while you could say that this type of housing was once in a bubble, it is undeniable that it is no longer in one; financiers are being very cautious about the projects they invest in and if they decide to provide funding for such a project they have probably done their homework.
When it comes to the cost of housing in the area, the reason housing is so expensive in Boston is simple: lots of people want to live here!
The solution is not rent control, it's to build tons of more housing! As much housing as the market is willing to supply of whatever type they are willing to supply. Government planners should not be setting the price or type of housing any more than they should set the price of your car.
If I say you can't sell books for more than $10, two things will happen: The most talented writers will find other jobs, and the existing books that are sold will go down in quality as content is recycled to try to keep turning a profit.
Similarly, if you try to say that every book must come from someone with a PhD, be at least 500 pages of 12 point font, and the author must donate 15% of his revenue to charity, the price of new books is going to skyrocket and the dearth of cheap new books means the used book market's prices are going to grow disproportionately too.
That's what we're doing with affordable housing quotas and "community benefits" in each project, excessive (in some cases) building and fire codes, cartelized union labor, and density restrictions that are lower than the market could sustain.
Let people build as much and as high as they want of whatever type of housing stock as they want, using whatever labor they want, without making them provide "benefits" (and do a cost-benefit analysis on some of the building code stuff).
Guess what would happen? Lots of building, lots of new property on the tax rolls, cheaper housing for all. Then, if you want, tax the bejesus out of it to pay for whatever public services/benefits/section 8s you might want.
You get the same result or better in "public benefits", but you do it in a much more open, transparent, and economically efficient way.