I bought pharoahe's internal affairs album for about 30 quid about 5 years ago. Love that joint and it was worth it. Even thought I've lost it again.
I saw a copy of that album in HMV, got ODB's nikka Please album that day instead. Great album but man I wish I bought Internal Affairs that day aswell, at the time I didn't know it was gonna be out of print so quick. This wasn't long after both albums came out (99-2000 I think). Probably won't ever own Internal Affairs now.
I've got original copies of Warcloud's "Nightmares That Surface From Shallow Sleep", "Smugglin' Booze In The Graveyard" & "Pro's Lab" bought directly from him & Professional. They were CDr copies but that's how they came out, I don't think there's many of them in the world, bound to get something back for them one day, CDr or not. Can't remember what I paid, wasn't crazy money though.
Paid $45 for 9th Prince's Grandaddy Flow album aswell (original, not the re-release), that might be the most I've actually paid for an album. [EDIT: Just done a little bit of research, only 2,000 were ever made, that's gotta be worth something I'd hope.] I've got a good few albums worth a bit of money though.
Shoutouts to unopened CD's of Nine Livez.

Them shyts going for over $200 each on Amazon, might have to cash in soon.