Are dealers prices fairly negotiable
Motorhomes are HEAVY. You need a big gas engine or a diesel to move it...
Some dealers have huge prices and lots of room to bargain. Some (few

) charge what its worth and stick to that. You must do your homework and find out exactly what the unit you want is worth. Offer much less and bargain up to that point and no further. These things depreciate fast, so you don't want to pay more than its worth to begin with.
In the past, NADA seemed better for buying (lower values) than Blue Book. If practical, get quotes from both and use whichever is lower. It may be worth buying the latest books from 1 or both of these companies so you have them at hand when you run across a possibility. If buying from a dealer, I would shoot for no more than halfway between wholesale and average retail. If buying from a private party, I'd try to get it under wholesale.
If you are paying cash, dealing on the price is your only option. When I go this route, I always talk 'out the door price'. Amazing what unexpected charges there are on the bill if you don't do this.
Financing gives you more things to deal on, but there are also more ways you can be taken. Have financing lined up before you sit down with the dealer, so you can tell if what they are offering is a good deal or not. Check the paperwork carefully, as 'errors' have been known to creep in. Never sign a contract to buy which is not contingent on financing. I haven't heard any cases with motorhomes, but car dealers are famous for selling you a car, then telling you that you didn't qualify for the financing and now are on the hook for a higher interest rate than you thought you agreed to.
Once you get past the saleman, they take you to the finance office, where the real money is made. Watch out for finish packages, special safety and security options, extended warrantees and the like. They are sometimes worthless and always way, way overpriced. For instance, $2300 for a paint/fabric protection package which they were down to $1435 on when we stopped bargaining (because I can't imagine it costs them more than $150, and that's mostly labor).