Unfortunately for you, the folks who say it shouldn't cost more than $275 do not have a gun to sell you at that price. There is an E*Bay type auction site that is a gunbroker (hint-hint). Using them as a benchmark, anything in decent condition is going to run you $350+/-, plus shipping, plus any FFL fees. Call it $400 out the door.
Unless it belonged to John Dillinger and the guy can prove it, $575 is too high.