Hi boomer and welcome.
As others have already replied, quality in the RV industry is very inconsistent and even the more expensive models often suffer from production defects. There is no reliable data, but all the manufacturers produce some "lemons" and some think the frequency of lemons is in the 10-15% range. Furthermore, the RV manufacturers leave it to the dealers to sort out defects prior to delivery, and few do that very effectively. Basically they let the customer find the problems and bring it back for repair. And such repairs are often lengthy in time, even if simple in nature.
The higher priced models are made with some better quality materials, more rigid chassis, and that sort of thing, and often have better workmanship under the skin, e.g. well protected and labeled wiring, plumbing shut-off valves, better cabinet construction, etc. RVs are extremely price competitive, so if there is a notable difference in MSRP for similar size and equipment, it is a safe bet the cheaper one cut corners somewhere to get the price down.
Finally, the market for travel trailers is dominated by price-sensitive buyers. Those who are willing to pony up extra $$ usually also want 5W trailers, so that's where the better built models are mostly found. They still suffer from the lemon factor, though, and there is still a range of prices and design quality.
Everybody wants 'quality', but "Airstreams cost too much" is the near universal cry. They aren't perfect either, but they are generally well built & equipped.