560SELs can be had for as little as $2500, but it will need a LOT of TLC. I've seen some pretty decent examples for $7000 or so, but they still needed to have stuff done to get them really up to snuff. Values vary widely thanks to the variety of condition/etc.
So, a good clean car that has been brought right up to tip-top condition is going to be a $10k+ car.