I cannot speak of personal experience with RV tires and the weight they carry, but...
I have bought many tires for my other vehicles over the years, most exclusively from Tire Rack. I don't blindly buy the cheapest tires, but I always buy economy-priced tires. Some are well known brands, some are not. What I can say is that unpopular brand tires have done just as well for us. When it comes time to replace our PC tires (please don't ask me how old they are), I will shop in the same manner. I won't "need" to get Michelin's, but I could see myself paying a little more to get them.