Michael,
It is a great book (one of my very favorites in my collection) but I don't know if I would ever pay $200+ for it [I agree that it doesn't look to be had for less at this time]. It is far more than just Prairie Grove and is extremely valuable. However, if you are only interested in PG, you might just want to wait until Fall/Winter when William Shea's book is rumored to be coming out. In the meantime you could always just borrow Banasik's book through interlibrary loan.

Drew