Of course it is a good starting point. That is exactly why dealers put the information in the ad. While paying cash for the RV is a wonderful thing, most people will never own one if that is the way they have to buy it. It is surprising for all vehicle sales how many people show up to look at them without a clue as to what the payments will be. Having a good idea of what you can afford under what terms before you arrive at the dealership will help you stay on point and keep from falling in love with more RV than you can really afford and making a huge mistake.
The key is to know your limitations, do your research, and setting your parameters before starting to look. I have watched far too many people get carried away and decide it is only another $100 a month more to get exactly what we want. Often that $100 is the difference between practicality and falling into the deep end. Decide what you can comfortably spend in cash and payments before you go and stick to it.