Cheap is a relative term. To a fellow with a $30k RV, $20k is cheap. To a fellow with a $120K RV, $100k is cheap.
Generally, a more expensive rig is heavier and better built using better materials. Some manufacturers, use the same frame and construction, just add some fancy electronics, slap on some bling, charge more and call it a high end RV.
For an example, our 5er in the signature has a 14" high powder coated frame, dual pane windows, heavier furniture, all wood cabinets, residential frig, three axles, Mor/Ryde IS suspension and the list goes on. The GVWR on the trailer is 19,000#.
Our is relatively high end, but to someone with a New Horizon or a SpaceCraft 5er, ours is a cheap RV.
Ken