My guess is Coast changed their design and your dealer either didn't realize it or they figured you wouldn't catch on.
Either way, if your contract states 60 jets, don't let them out of this. Especially considering I used to sell Coast, and even in Canada, $15 grand is a ridiculous amount of money for one of their tubs. The only one of theirs we ever even sold close to that was the TV/Stereo model, and even that was "asking price."
Good luck, Erin, and I hope it all gets worked out.