If the dealer came down that far without much effort, there's probably plenty of profit still being made. Although the overall market is strong, it seems to me that demand for used units is soft because of the high supply of new units- this is typical for most big ticket purchases.
Negotiate up from 31 and see where they land- just because you feel Bigfoot has a great name doesn't mean they have to know you're locked into that brand. Pointing out a handful of other units at lower price points will help them flinch first. Good luck!