There are a lot of factors that can determine the best deal. Obvious things like distance to the dealer factor in. If you have to drive 10 hours to save $200, that isnt really a deal because of time and fuel cost. What time of year matters as well. You can watch the same RV from the same dealer fluctuate in price by $20k (or more) over a 6-9 month period. For example, in the spring it may have an advertised price of $65k (just making up a number). Because that is when the RV season is starting, so that excitement means people will pay more. You may see it rise up to $70k (or more). But then in the fall, as the season is winding down (and the new models are arriving) that same unit from that same dealer will be advertised for $45k. If someone were to finance that for say 15 years, that $20+k difference in price is probably $45k difference in out of pocket cost with interest, etc.
Fortunately the internet has made things a little bit easier. As others mentioned, a site like RVTrader can show you a wide range of prices, for what seems to be an identical unit. You can also use websites of large dealers like Camping World and see what their units sell for (and you can set it to a distance near you, or nationwide). Use the information to your advantage. Some dealers list all of their units at MSRP. Some list them with MSRP slashed out with their sale price, etc. Some have MSRP listed, slashed out, with a "contact us for best price" notation.
An example I will give you from our most recent RV purchase. We are no longer Forest River owners but we like the forum and the members here and there is more than enough crossover from one manufacturer to another, so we decided to stick around. But anyways, we started looking in January of this year. I would say we were passively looking. Meaning if we got the deal we wanted, we were ready to buy, but ONLY if we got the deal we wanted.
We visited a dealership in Danville VA that we had purchased from previously (twice, including the one we planned to trade in). They had a price of $85k advertised. We looked at it, we liked it, we sat down to discuss numbers. They gave us their sheet and it still said $85k. Which was about 17% off of MSRP. Needless to say we didnt purchase. The price we were looking for was more like 30% off MSRP. There were other dealers that had that price point, but we didnt like those specific units for one reason or another (for example, one had a huge gouge in the living room floor, through the linoleum and gouged out some of the plywood floor as well, they said they could repair it, but we just werent interested, looked like someone dropped a fridge on it or something?). We were willing to pay $73k in Danville, because we had previous dealings with them (but they were bought by a much larger corporation since our last purchase). They gave us the whole sales spiel about how they were practically losing money giving us this "great deal" (because they were gonna give us $23k for our trade, which is exactly what we expected to get from them, it was the sales price that made the difference). Anyways, to my point about price changing, we kept looking at all of those models from many different dealers. And we saw them go down to as low as $67k until the season was about to start, then they all went up to the $80+k price range. Then as it got to summer the prices started coming down again.
We found Camping World had one that they cut the price down to $63k. We called them, they still had it, the next day we drove 5 hours to see it, and made a deal. They only gave us $21k for the trade instead of the $23k that the other place had offered, but the sales price was $22k less, so I wasnt worried about it.
The best part, that original unit that we looked at in Danville, is still on their lot. If they had gone down to a reasonable number (30% off MSRP) we would have bought it. Instead we got ours (with a few upgraded features as well) for 42% off MSRP. They have begun reducing their price, and they are down to $79k from their original $85k. But it still hasnt sold. Because most people, like you, have the ability to look at the internet. And see what the price point is for comparable units.
My overall point is use your resources, be patient, and wait for the right deal. And be reasonable. Obviously you want the best deal, but be realistic about what deal you think you can get. Some dealers really want to make a sale and they will offer prices that show you that. Others just want money, as much as they can get, and they seem unwilling to negotiate at all. Even if they do, I am leary of those places because they tend to be the ones that suck at the "after sale" needs of a customer. In Danville, they had their price, and that was their price. They wouldnt budge from that. Even though we knew there were others at the price we wanted, they still didnt want to make a deal unless it was their price. If we didnt want to pay that we could take a hike, so we did. And they still havent sold it... But we enjoyed our new RV for the last 3 months of the camping season.
