My neighbor sold his acct for 3500, but he.was In one of the first few guilds to clear naxxMany people cashed in big time on Grand Marshall. We had a circle of grinders. It took a few people to keep the account online and playing 24/7 and you'd make it without too much trouble on certain realms. It was all about staying logged in.
That was the only way to make 2k-3k that I know of. A raid geared account was never worth all that much even back in the day.