A few thousand for the trailer and then price out the RV appliances.
Slide mechanism, He's got a couple grand just in wood. Wire, glass windows, A/c units, etc.. etc...Have you price diamond plate? (which is not in his cost spread sheet). Just doesn't add up. If you check his spread sheet , plenty of items missing and the prices on some items, are well............. Really unbelievable, IE: RV window $10, Tub surround $10, Skylight $10, 22 rafters for $22...
Sounds like a fisherman. Other than that , he did a awesome job and still saved himself a bundle.