Look at KEH to see what they're getting for them, remembering that they grade condition very conservatively, so the EX grade is usually fairly close to flawless, and BGN is usually what some ebay sellers would call "minty". For sure don't pay more than what they want for a camera in truly comparable condition.
I'm surprised at the prices for the original 645. They seem to have gone up quite a bit over a few years ago, when I last monitored KEH's prices on them.