When I bought my Class A 25% off seemed to be the norm across the board but negotiating on a truck camper is going to be very brand/dealer/location specific and I highly doubt any dealer is going to give anywhere near 35% discount on one.
TCs as a whole have a lot less built in profit then other types of RVs due to simple economy of scale in their production.
Smaller brands need to make more profit per unit, so less negotiating room on price.
Same goes for a smaller dealer, as they have to cover operating expenses on say 20 units a month instead of 100.
Further from the factory the more it will cost as shipping goes way up. That's why there are much fewer TC dealers on the East Coast, as most are built on the West.
If the dealer only sells TCs they will cost more then if he also sold other types of RVs that allow him to spread his profit margins around. Selling a couple $200K Class As at or near MSRP allows for a much lower profit on that TC.
Are you willing to settle for a year or two older model that has been on the lot for awhile? If so you can usually get a pretty hefty discount on those.