I had a similar problem with John Eagle Honda. They quoted me MSRP to order one, and after checking around, I figured I wouldn't do much better. Then, when we started filling out the paperwork, they said they had a mandatory sealant package all their vehicles required - for $499.
I argued with the salesman, and he said that they required it on every vehicle for "extra protection". I had just bought an Acura at John Eagle Acura, and they include the paint sealant at no charge. So, I told him that it's great if they want to offer extra protection for their customers, and they are welcome to throw it in like the Acura dealer did, but I am not paying for it. They finally relented and took it off.
The way I see it, you're not really getting a good deal on the car if they force you to buy options that you don't want. Paying MSRP for a car was a big enough psychological barrier to get past, there was no way I was going to pay another $500 for options I didn't want. These Honda dealers better watch the cockiness, because it won't be too long before other vans catch up to the Odyssey.
BTW, my wife and I were also looking at the Toyota Sienna, and this is one of the things that turned me off about the Toyota. We were looking at an XLE with the luxury package and the video system - not exactly a stripped vehicle. However, every Sienna we found in town also had the towing package (an extra $300, not too big a deal), and something they call the "Extra Mile" package, which was a bunch of useless crap like window etching, wheel locks, and a tire warranty. They were charging $1300 for that package. I found out that this is something that the Gulf States distributor always adds on, and that it would be nearly impossible to locate one without the extra $1600 in options we didn't want.