If they change the price last minute can you renege on your side of the deal and get your money back and cancel?
This is sort point for me. I once custom ordered a BMW with the exact options I wanted. Made a downpayment. Waited 3 months for it to arrive taking the bus to work and getting rides home from friends. It arrived at the dealer and they sold it someone else and then told me I could order another if I wanted. You can probably imagine the rage I felt.
Some dealers won't do this, but you'll need to put in some work to find them.