The CBO scored the House version of the healthcare reform bill -- with the public option included -- and the price tag is almost exactly as predicted. And it would be paid for by reducing inefficiencies in Medicare and Medicaid, along with an additional tax on wealthy Americans.
The page describing the public option can be found here, and regarding premiums here and here.
Also, it's worth ballyhooing that there's an actual healthcare reform bill with a public option ready for a vote in the House. That's historic.
UPDATE: From the comments. The public option in the House bill doesn't kick in until 2013. So far, I can't find an explanation for this.
UPDATE 2: The Health Exchange won't begin until 2013, which means neither will the public option. Still no reason why.
UPDATE 3: I'll have a second related post up shortly, but this from Digby and Jonathan Cohn answers some questions:
Cohn says it takes longer to come fully online than he would have hoped, but that is likely due to the arbitrary budget cap.
The "public plan" is actually several public plans, all of which will be available as soon as the plan is operational. (This should not be confused with the HCAN requirement of "available on day one" which was in response to the trigger option, which is not included. It was never intended to be a requirement that everyone be covered the day the bill was signed, which would be physically impossible.)