I already owned the truck......and many use their trucks for more than just RV'ing/Camping. That's where the benefit of the TC comes in for some of us.
My truck is one of my biggest tools in Alaska. It takes garbage to the dump, tows boats, brings gravel/goods to the property, gets and transports firewood and hauls heavy equipment saving me a big chunk in the rental costs. Adding a truck camper to the mix just extends the usefulness of a vehicle I've already got tons of money into. 15 years and 130K miles of use so far. I won't mention how much I've got into it.....but it's been paid off for years, and despite the numerous upgrades....still costs considerably less than these newer models. In many ways, mine performs better also. If you are buying a truck....just to RV in a TC, then yeah...I'd consider a specialty build class C or something.