You can also PM with members of the Owner Groups that have made recent purchases, and see if they'll share the percent off of MSRP they reached upon purchase.
20-25% seems to be a nice target goal
! But, it is brand specific, and time of the year can matter too. Going into the 'off season', especially in winter prone areas, can make a difference on slow down at the dealers.
I've also heard that some buyers have obtained Show Prices, from large RV shows.
Gary mentioned the services that I know of, but I have never heard of any results from these services.
One angle I've also seen accomplished. Is to know the coach, model, options that you desire. Prepare a Request For Bid document with this info. Choose dealers within the region that have good reputations, and that you would be willing to travel to to wrap up a deal. Send this request to bid to the attention of the Sales Manager. Let them know this bid is being sent out to other dealers for bid too. (Don't mention names.). And, if you want a extended warranty, and financing involved with this, state that up front too. (Sometimes they can shuffle things around, knowing the warranty and financing profits are involved too.)
Best of luck to you,