The risk is there end up being more regulation on affordable housing because Act 250 comes into play with 10 units or more, and developers are generally going to want to build more than 10 cheap units at once (whether in an apartment building or single family neighborhood). Once Act 250 kicks in, it is a uncertain bureaucratic process which could lead to years of disputes (which adds to cost), and even ultimately shut down the process. It's much easier and less risky to build one or a few luxury houses because it is less regulated.

I think lots of developers would prefer to make 20 cheap homes than spend the same amount on fewer luxury homes, but it's just a risky process with act 250 on top of other permitting and zoning. Making tons of cookie cutter houses or an apartment complex is, in many ways, easier than making a handful of luxury homes, since you can much more easily reuse material and designs.