I guess it would depend on what sort of RV you are looking at. Not all brands cross all types of RV. For their travel trailers I would hazard a guess at their Rockwood Signature Ultralite being the top of the range. For fifth wheel RV's I'll stick my neck out and suggest that Cedar Creek is the top of their brand list but then I do have a biased.
Richard & Diane
2014 Cedar Creek 38FL
With an F350 DRW
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Richard & Diane
2014 Cedar Creek 38FL
2016 F350 Lariat CC DRW
Retired Metropolitan Police (UK)
If you're wondering about Rockwood specifically, I'd say it's a medium quality trailer line along with the Flagstaff brand. I'd say Wildwood and Salem are probably their "value" brands. Not too sure about their other brands.
I would assume so, every manufacturer is like that, you have top of the line, midgrade and then the entry level. That way a manufacturer can offer a wide array of products to meet the price demands of consumers.