I like to put them on the spot myself. When we bought my wife's Lincoln, I went ahead and let them think I was broke and I needed the loan. After we had done all the negotiating and they were ready to close, I pulled out my check book and wrote them a check for the price he quoted us. They lost it. It turned out, they were planning to make almost $2000 on the financing. They did hand me back my check and said they couldn't do it. I was surprised, usually they gripe about it but stop me before I get to the door. (I have done this before) I ended up financing $7500 (the minimum they could write) and paid it off in 3 payments, the minimum I could do. (1/2, then half of that, then the balance) The interest was about $150 using the funny way they compute it
With Obama's $4500 for the ragged out F150 I traded, the $450 for the scrap value of the truck and the tax credit for the closing fees, it was a pretty good deal. ;-)