As best I can tell from checking a few industry sources, average trade-in value will be in the $22-23k neighborhood, not including the value of any add-ons, and retail around $28-29k. The days of getting what you paid, or anywhere close, when you trade in your Harley are just a distant memory. These days your Harley depreciates the moment you sign the contract, just like other vehicles. It's something to think about if you're the type to tire of a vehicle quickly. Paying premium prices for stuff that depreciates is not a highly recommended practice, especially if you plan to trade every year or two.
You don't mention if there are any other dealers you could work with, but if there are I would suggest getting some numbers from them. And in the current economy and motorcycle market I wouldn't even consider paying a penny over MSRP for a new bike. Tell them to take the bogus "extra profit" charges like prep and other fees and put them where the sun don't shine. If the dealer doesn't want to give you a decent price for your add-ons, take them off and put the bike back to stock. You can use the parts on the new bike, or sell them on ebay, or whatever. I'd much rather give them away to a friend or acquaintance versus letting a dealer have them for nothing. Btw, as noted by others you will be better served financially if you sell your bike privately versus trading it in. If you split the difference between average trade-in and retail and use that as your minimum private sale price, you'd be looking at around $26k plus whatever a private customer would be willing to pay for the Tour Pak and other extras. Another question to ask yourself is how much is it worth to you to not have to deal with selling the bike. Trading it in is definitely more convenient, but you pay for that convenience. Nothing a dealer does is out of the goodness of his heart, he is in business to turn as much of a profit as he can. For some of us it is worth something to not have to get involved with private sales and possibly unscrupulous people or scams, but for others who buy and sell stuff all the time the private sale idea can be well worth the extra time and effort.
What's so special about a 2012 that makes you want to get rid of a very low mileage 2010 that you've already customized to your liking? If it's the audio stuff, you can add that sort of thing to your 2010 for one hell of a lot less than the $12k plus you stand to lose on a trade with that dealer.
Jerry