Are public clouds cheaper? Are private clouds cheaper? Under what circumstances is one form of cloud more cost-effective than another?
I don't think we'll ever have the definitive answer, but there's some interesting new data to contemplate, courtesy of the recent EMC analyst day.
For most people doing IT at any reasonable scale, the number shows that private clouds can be significantly less expensive than public alternatives in many situations.
And that's *before* any concerns about availability, security, regulatory compliance, control, etc. are factored in.