Well, first of all, let's agree CW is a giant rip-off outfit. But, a lot of other so-called RV specialist stores are equally bad. I've had the misfortune of encountering several.
As to EPDM (rubber) roofs - this stuff is virtually industructable. We used it to line five miles of a water supply canal north of Tucson 25 years ago and it hasn't leaked a drop in the last 25 years.
Yes, it needs to be cleaned and the edges need to be sealed as part of normal maintenance, but it isn't so delicate that a certified technician has to do it. This stuff is tuff and it will last the life of your coach unless you leave your coach out in the desert sun for twenty years.
As others have said, the RV "specialists" like to climb up on your roof and look for loose change.
Al & Sue w/T-Bone & Rosco
Go Devils Bus, 1994 8.3 Cummins, Spartan Chassis