Interesting article on Mike Berken's "The Domains" website about the sale of the domain FundAnyting.com for $2500. and the eventual use of the domain.
Mike's bottom line: ~I'm not Monday morning quarterbacking. I'm telling you to do a better job of sizing up the utility of your domains before selling.
Worth a read.
I've never experienced seller's remorse and I've managed to sell generic domains to a few very LARGE entities. Never priced a domain based upon buyer's wallet. Always priced based upon my best assessment of value.