No different than if you were looking for a trailer and needed a hitch. Hitch is going to cost what it costs and not proportionately priced or related to value of trailer your pulling. Nor anything else you might need-ie wiring, bed mat, etc.
Best option cost wise is looking for used tiedowns to fit your truck.
They are required to carry a camper.
If you only have x amount to spend-simply need to factor in what its going to cost to safely mount it to find what you can actually spend on camper itself and still have enough to use. As long as you keep the truck its a one time cost for the tiedowns.