[richardew]

Here is my calculation. They came up with $658.20. My calculation is a $1.13 different, basically the same. As you can see, you are paying $88.14/month interest on the balloon amount no matter what they are telling you. You made one mistake in your calculatons. The amount that you are financing is the msrp - down payment - balloon. You forgot the $5000 down payment.
msrp $56,807.64
down payment $5,000.00
msrp - down pmt $51,807.64
ballloon $21,586.50
amount financed $30,221.14
rate 4.90%
term 5

payment on amount financed $568.93
interest on balloon $88.14
total payment $657.07