I've seen some older ones on Ebay go for less than 10K. I paid 12,500 for mine as a demo.. At the time the MSRP was $15,900. With only 123 miles on it, it was new enough for me!
I LOVE the Blue colored one, that is what pushed me over the edge into buying one, but I got a black one instead..

I will get it painted the way I want one of these days..
I think the Rocket is more of a nitch market bike than Triumph had planned on. I LOVE mine and have 19,000 trouble-free miles on it this past year. I'm not worried about depreciation, as I don't intend on selling anytime in the near future anyway.