Evil Avatar came across a great little cost calculator for determining how much each of the next-gen systems cost. It takes into account the various features and accessories such as headsets, rechargable controllers and more. It also asks you a series of questions such as, "Do you have an HDTV? Does your TV have HDMI? Do you want a High Definition Movie disc player?" Selecting a lot of items in the 'need' column such as wireless headset, 120 gig drive, and others will really drive up the cost.
Here's what they came up with for low-cost and fully-loaded solutions:
Xbox 360 Core + Memory Card = $339.91
PS3 (60 gig) = $599.99
Xbox 360 Elite + goodies = $833.61
PS3 (60 gig) + goodies = $790.36
Go Ahead, You Give it a try