good point Dan, one I have been pondering for some time... here are some problems I have identified:
1. hardly anyone selling these tapes actually listens to them
2. "near mint" "appears unplayed" - next thing you know I get a tape full of mold!!!
3. sometimes, one side appears mint, while the other is utterly useless
4. I have even bought tapes where something else has been taped over the original recording (no doubt refunds were issued, but still)
5. there appear only a handful of "reliable" tape handlers on eBay, those are the ones I usually stick to...
6. I typically stay way from dubious claims such as "master tape dubs" - quite frankly I am (almost) sick and tired of hearing that bullcrap, present company excluded of course! :)
7. pre-recorded tapes fluctuate in quality in general much more so then vinyl, in my experience
just a few points... also, I have noticed prices to have gone up considerably on some titles, as the "tape" boom continues or gets more focus or what have you...