Skype’s new owners — Silver Lake Partners, Marc Andreessen, and company — are getting a company valued at $2.75 billion (according to former owner eBay) with 405 million users. That’s $6.79 per registered user, and a little over five times Skype’s 2008 revenue of $511 million. Skype grew by 44% in 2008. So did the sale — in which eBay retains a 35% stake in the company — come cheap or dear?