As someone mentioned, MSRP that the dealer claims is not always real. So rather than worry about how much off MSRP, worry about actual selling price. Google the brand and model you want and see what many dealers are selling it for and let that be your guide. I was fortunate and had access to real factory MSRPs and caught a dealer overstating the MSRP by many thousands of $$ to make his discount look great. When exposed, he stopped communicating. Anyway, my deal was 32% off factory MSRP with a custom order that included un-listed options, so I had to approve a factory printout prior to the build being scheduled.
Delivery costs are pretty much fixed by distance from the factory. You can buy from a dealer right next to the factory and have the unit delivered to your house. Delivery cost will be almost identical to what a local dealer will charge you. The only way to save on delivery cost is to pick up the unit yourself. And you can do that even if you buy locally, you are just the towing service rather than someone else, but the unit isn't yours until after PDI and papers are signed.
Some dealers think they are the only game in town and don't want to negotiate. Fastest way to find out is to get multiple quotes from 'local' dealers and internet dealers, then set your target price and give everyone a single chance to respond. My 'local' dealers were 70 to 180 miles away, two were competitive with internet dealers and matched or beat my target price, one still quoted 20% over my target price. Their loss, not mine.
Finally, my rough understanding is that the dealer's cost from the factory is based on sales volume, so a high volume dealer near the factory has no advantage over a high volume local dealer (excluding delivery cost). Also it is my understanding that this is not based on brand volume, but model line volume. So a dealer selling lots of brand XYZ pop-ups isn't the best place to get the lowest price on brand XYZ toy haulers.