Has anyone ever come across a Fender JP-90? I want to know what you think of them, and what do you think they are worth in good condition?

All I can gather is its Made in America, has a standard jazz and p bass pickup combo, and has a Jazz-like neck.
Well Enough Alone
The JP90 was made for the metal crowd, though it is by no means just a metal bass. It just looked more "modern" than most Fender Basses. It was made in the U.S.A. and was, as I recall, a good bass. Check this out for a demonstration of one being played in a non-metal fashion:

i've played a JP-90 before and i liked it. built 1990 to '94, P/J p-ups, poplar body, rosewood fretboard. top money is $500 for an excellent example. in today's market, i wouldn't pay more than $300 for one in perfect condition. not a bad bass.
IMHO, price is a subjective thing. But on the whole, US$400.00 isn't at all bad for a U.S.A. made Fender Bass. And who knows? When you become a rich and famous bass god playing it, everyone will want one and it will increase in value.
That pickguard is ugly as sin.
Try talking them down to around $350 if you like it and it's in good nick.
Lol that would be cool, but I am no dedicated bass player. I am using it for recording only pretty much. I am a guitarist/singer/producer and I'm trying to get something with pretty good tone without busting my bank.

Of course if I had a lot of money, I would go for something awesome like a musicman but I'm on a tight budget for now.
Well Enough Alone