From Dar.fm’s FAQ:
Q: Wait – is it $39.95/year or $40/year?
A: Officially it’s $39.95 because some MBA student showed us a spreadsheet explaining how there are people out there who if they see “$40” will say, “No way – that’s much too expensive!” But if they see $39.95 they’ll round down to $30 and think “Man, that’s barely more than a Starbucks coffee, what a great deal!” and then type their credit card into the system. We think he’s crazy but his Dad put some money into the company so we’re humoring him.
Actually looks like a cool service, and something I’ve pondered writing myself for years. Might need to sign up.