Not an expert and not in the states but the last time I looked into buying one, they where being sold to private buyers (with government approval) for around 100 000€ an in good shape. I remember a few was released by the South African government in selvage condition some time ago and the rest that where in serviceable shape where updated to the newer specs and given a new lease on life in service.
The Casspir is also my APC of choice but its going to be hard to find.
Again, this is just what I remember, so don't be put off, things might have changed. If you do happen to find some good cheap ones, please let us know on the forum.