I think one needs to step back and look at this more objectively. If it wasn't for the current situation with the society right now people would not object to this. Some of the most glorious churches in the world, certainly in the US, were built by the poor, struggling to feed their families. Even the very beautiful, but simple country churches scattered around came at a great cost to those who built them. We mustn't start acting like protestants and using their arguments, just because we may be upset with an unrelated decision by the Superior General.
I didn't think too highly of this project idea when it was first announced, before the present SSPX crisis. I agree with others that the needs of the SSPX seminary could be more than adequately met with much less money. When there are still faithful who must attend Mass in hotel rooms, does the district really need such an expensive seminary?
That is comparing apples to oranges, though. They are too different things. Local chapels are supported locally, at least primarily. When that particular Mass center can support itself financially, and afford to build/buy a church, then it is free to do so. This is the case regardless of affiliation (Society, Sede, Independent, Diocese, etc).
The larger entity (District/Diocese/etc) is responsible for the overall continuation of that entity. One may certainly have concerns that they are not properly using those funds, and I would bet that every public/religious construction project has its critics. But I disagree with the notion that the district has a responsibility to build everyone a local church before tending to the needs of the seminary, which is absolutely necessary for the continuation of the society.
Again, I am speaking in terms of principle here. The particular situation may change things, but in principle I don't have a problem with it.