For reference, I bought the old popup for $2k, and spent around $4k on steel, the axle, wheels, tires, jacks, propane lines, paint, harnesses, the winch (to raise the top) and a LOT of miscellaneous other repairs and upgrades that had to be done. That includes several thousand paid to my buddy for his labor, without which I would never have finished this project.
WAAAAAY cheaper than paying 10-15k on what is structurally an inferior product. All you miss out on is some creature comforts of the newer models. All in, these old popups are a far easier project to tackle than restring a car.