That's a good way to look at it, Ken. The loan for my 03 was 3.33%; it cost me ~$2,700 to finance my truck.
Can you take the rebates and still finance what's left through Ford Motor Credit, if they're competitive? You won't get the 0% deal but you could still get, say, 4.9% or less. Otherwise I think most dealers work with several lenders to get competitive rates.
And I think many don't realize that the interest rate is negotiable, if your credit is good enough.