So, how is it that the SSPX can ask for money from its parishioners? The rich are asking the poor for donations.
The same sentiment that is expressed in this OP could very easily (and probably was) used back between 1880 and 1920, when many of those older Churches were built, i.e., “How can the Catholic Church expect poor immigrants to pay to build huge churches when the Vatican is worth millions in assets?”
I don't think it's the same situation at all.
The Church wasn't in crisis back then. Also, those immigrants scrimped and saved for a glorious church IN THEIR OWN BACKYARD. So if they stayed in their hometown, they would be sure to benefit from that church until their death, and their children and grandchildren would benefit by it as well.
I don't think poor people dug nearly as deep to build a seminary on the other side of the country.
But even if they did, it was because there were DOZENS of TRUE CHURCHES (not oratories, chapels, or rented hotels) in their own hometown. So they could choose to be generous to help the formation of priests, the foreign missions, or Peter's Pence.
Compare that to the SSPX today. Some chapels (Austin, TX) don't even have a permanent location of their own. Others are in dilapidated old buildings that used to be protestant churches. And let's not forget about all the locations where there is no Mass offered at all!
Today, it could be successfully argued that the SSPX doesn't have the money to be building a "fancy" 100 million dollar seminary. They should be taking better care of their parishioners (souls) instead.
As one person so eloquently put it, "You don't build monuments during a time of crisis."
When everyone is floating around on the open sea in dozens of lifeboats, you don't waste your time and resources making one of the lifeboats into a "conversation piece". You spend ALL your precious time and energy on the care of souls -- finding more food and water, repairing the various lifeboats, trying to find more survivors floating on driftwood, etc.