Final Report: I won the good stuff!
I got the Prizm V with the Prizm IV coil for $100. Basically I just held my hand up and waited for everyone else to back off. They probably didn't even know if it even worked like I knew, I never saw anyone else actually take it off the wall, so if they were going by the coil only they would have assumed it was a Prizm IV as 19blockhead64 inferred. If you detected around here you'd know why the smaller coil is preferable to use, though maybe not as salable that way.
I picked up the Whites Bullseye 140mm for $10. I might have jumped in too soon, I probably could have got it for $5.
Lastly, I won 3 digging knives for $5. One is a Craftsman bulb digger, the other two are real heavy knives with motorcycle grips on them. Why didn't I think of that before?!? I put some batteries in the detector and went out and found an old whatzit, a new quarter and a deep soda can before it got dark. Everything seems to be in good working order. Woohoo!