A base LS-model Camaro, equipped with the potent direct-injection 3.6-liter V-6 and a six-speed manual transmission, starts at $22,995 - about $1000 more than a 2009 Dodge Challenger SE and $2000 over a base 2009 Ford Mustang V-6.
If you insist upon an eight-cylinder car, the Camaro SS - equipped with GM's 6.2-liter LS3 V-8, starts at $30,995 - higher than the Mustang GT, but similar in price (and content) to Dodge's Challenger R/T.
So when can you get one? GM doesn't anticipate shipping production models until spring 2009, but as of today, you can place an order for the new muscle car. In fact, GM's produced a convenient PDF form for you to take to your dealer and spec out your car.
If that doesn't provide enough background data, try GM's Online Order Guide (found here). Though it won't let you price out your Camaro, it does reveal a considerable amount of information (i.e. option codes, dealer accessories, etc.) not found in the PDF guide. For instance, we're seeing mention of a Hurst short-throw shifter, an Inferno Orange interior dress-up package, and several different exterior stripe packages that don't appear on the PDF document.
Check out GM's PDF guide here, and the Online Order Guide here.