A friend of mine gave me his copy of Panzer Dragoon Saga back in the day, and tossed the manual because he dropped it in the ground outside of his apartment and it got wet. It wasn't ruined or anything, just wet. He was being an asshole that day, so I didn't feel like saying anything about it (he's the type of guy that just looks for any reason to get into an argument about anything). Of course neither of us have any idea it had a fairly limited run.
I purchased another manual to complete it a few years ago for about 30 or 40 bucks. I don't remember exactly how much, but it was awesome to have a complete copy of the game for under 50 bucks.
He gave me Burning Ragers and a bunch of other Saturn games as well. This is around the time the Dreamcast was all the rage.
My Popful Mail for purchase from EB for less than 20 bucks, and I'm pretty sure that goes for a fair price now. M.U.S.H.A. I just bought because I never owned it but friends had it back in the day. I bought my copy for maybe 20 bucks about 9 years ago, and that thing goes for ridiculous prices, especially around Christmas time.