They weren't hard to come by about half a year ago when I bought one. It came without a battery or AC adapter. I paid $256.
Edit - I just checked eBay and searched for "T61p". I found:
* A 4:3 T61p with an incorrect description for $500. That seems high.
* A 4:3 T61p missing its palmrest and other parts, auction only.
* A T61p in a T60 chassis with a QXGA panel, SSD and other upgrades for $1300. That sounds high unless you've tried to find a QXGA panel; they're over $400.
I've been trying to grab a 4:3 (1400x1050) T61 for a while off ebay as they're cheap and upgradeable to a reasonable spec.
Unfortunately I can't seem to find one :(