I dont think its even a matter of different product types, It seems more to be a difference by level or overall cost of product lines.
Since many interior items, water pumps, heaters, appliances etc, are the same across a wide variety of product lines from basic $12,000 tt's to $30,000 units the change in quality in large part is likely in the time manufacturing crews are given to assemble the materials, as much as its a difference in materials. Yes Glass exteriors are one major upgrade cost, bigger tanks or heavier axles add some, but the difference in cost and quality are as much or even more so a matter of the time crews are given.
And yes I talked of TT's ,but with a Class A or any other unit the same principles apply.
