If you know how to inspect one and don't need to buy the first one you see, you can buy a heck of a BP, probably with tooling, for $3k. Prices seem to be creeping up, or maybe it is a function of the fact that the dollar is going down the tubes (inflation). But over the past few years around here, a good BP with vise and probably DRO at auction tended to run $1800 - $2500. (Used DRO should not figure highly in the price, generally. But if it does end up all working, it is a nice bonus) Have seen a couple of really good series 2 sell for right around 3K if you can house a big one. 2 saturdays ago I was at a weekend auction (worst time for prices, because all the HSM's are out in full force) and a very well maintained older BP series 1 from the toolroom only use, with 42" table, faded paint, DRO, full set of collets, vise, some other toolholders & "misc" tooling went for right around $3K at Cornell U. (I seem to remember $2950, but it might have made it over the 3 mark, I was only half paying attention at the other end of the room).
OTOH, there are also a lot of junk BP's that are priced quite high. So you do need to be able to check it out in person if paying the larger amount. IOW, paying more to an unknown vendor, does not automatically insure a better machine.
smt