Ebay is Ebay, I have no idea why things sell for what they do. AFA the EZ-48v being a collectors item, NOT a chance, my guess is most will be junked within 5 years or less, they just aren't that well made.
Don't get me wrong, I love Panasonics and believe they(including the EZ-48v) can make excellent recordings and have features found on very few if any other DVDRs but personally I really don't like the EZ series. I've had quite a few and the only ones I believe are worth the trouble would be the EZ-28(basically a EZ-48v without the VHS side and a few of the EZ-48v's quirks) and the very hard to find tunerless EA-18(basically a EZ-28 less the tuner and most of the bugs on the EZ-28). Currently I have a EZ-28 which I use occasionally(IMO it's really the only Panasonic with a digital tuner I believe is worth owning) but personally I much prefer the pre '07 ES(and even better EH(with a HDD)) model Panasonics. The only problem with the pre EZ models is they don't have the digital tuner, which for some can be very handy. For a couple years I lived with a EH model Panasonic and a external digital tuner(after having tried many EZ series Panasonics and giving up on them) but currently I'm doing basically all my timeshifting on a Tivo HD and only use my Panasonics to offload(copy from) my Tivo among other things.
A couple years ago they couldn't give away the EZ-48v models, most of which were refurbished(read, someone tried it and promptly returned it because of all it's quirks and bugs) so I can't really explain why the sudden price increase on places like Ebay. I've been watching a EZ-48v
listing on my local Craigslist, it's been around for quite some time(although the seller keeps listing it as if it's fresh) but personally I wouldn't touch it unless it was in the $25 price range, and even then it would have to be close, no driving across town.
IMO Panasonics worst models would be, in order of worst:
EZ-47v, EZ-17/27, EZ-48v with a slight nod to the EZ-28. On the flip side, the best: EH-55, EH-50, EH-75v, with a big nod to the EH-59/69 which are wonderful machines but being international
have a few caveats for N. American use. The older pre EH series HDD Panasonics were also quality machines but they lacked full D1 resolution LP which is a major point for me so I shy away from them.