From fuel prices to tax credits, which hybrid pays you back?

Toyota Prius Base

Base Price (inc. dest): $23,535.00
Tax Credit  $0
Adjusted MSRP:  $23,535.00
Premium:  $3,425.00
MPG: 48/45 (city/hwy)
MPG Benefit: 18
Combined MPG: 46
Annual Gas Cost (15,000 miles, $4.20 per gallon):  $1,369.57
Gas Savings:  $880.43
Years to Payback: 3.9
EPA Pollution Rating: 8.0
Compared to: 2008 Toyota Matrix S
Base Price (inc. dest): $20,110.00
MPG: 25/31 (city/hwy)
Combined MPG: 28
Our Take: “Comparing the Prius is like comparing spots on a giraffe. We found that the Matrix offered the same hatchback bodystyle with similar power numbers, but 18 miles-per-gallon less -- yet more cargo room -- for around $3,500 less.”

Details, Price Quotes:
Toyota Prius