well, first off. i'm fairly sure its not legal for them to do that to you.. for them to take back a vehicle like that. once it is sold, it is sold. you fell into their trap. they were sad that they sold it for the price they did, but you know what, they shouldn't have sold it in the first place if they weren't going to be happy. the best thing you could have done is to contact a lawyer and ask them if it was legal for the dealership to do this. i would assume no. next thing i would have done is contact American Honda Corporation and told them what the dealership has done. They get really angry when dealerships are being shady, so they'll put pressure on the dealership to fix their ways.
another thing i hate doing is negotiating based on payments. i refuse to talk numbers based on the payment. i hate it with a passion when dealerships try and negotiate with me based on how much of a payment i can afford. if they don't want to deal with me based on actual selling price instead of payments, i walk away.
anyways, i'd contact American Honda and tell them about your situation anyways. It will hopefully prevent the dealership from shady practices. If you don't mind me asking, what dealership?
And you're right, the 72 hour cooling off period doesn't exist in California anymore.
Good luck with everything! And if I were you, the first thing I would do Monday morning is send American Honda a letter and an e-mail, and then send one to the Better Business Bureau as well.
Any pictures of the Odyssey? I'm sure you will be very pleased with the purchase. Hopefully, it's what you really want.