I agree that extended warranties are a waste of money on some product lines. I generally don't buy them on new cars, motorcycles and the such. However, my experience on the three RV's I have owned is that they have paid for themselves. There are just so many different systems to go wrong. It also helps to have a dealer that knows how to file for the extended warranty coverage. I have had things covered that I did not think was included in the warranty just because the dealer knew how to word the claim.
Also, the price is always negotiable since, as you point out, there is a high commission to be paid through various levels along the sales path.
For those reasons, I think the extended warranty on an RV is cost effective. As for roadside assistance, $95 a year for peace of mind is just good insurance in my mind. I surely cannot change the 22.5" tire on the side of the road and do not have a spare anyway. That is the main reason I carry Coachnet.