RV shows are generally good for seeing the variety of what is available. Most of them focus on new rigs rather than used, but I've not been to the Quartzite show. Prices are hyped, e.g. "Show Special", but rarely much better than you can get at anytime on the dealer lot. A typical new RV discount offer at a dealer starts at about 15% off MSRP and sometimes can be negotiated down as much as 30%, so the "show price" is mostly just advertising what is a normal price.
Used RV prices are not as consistent as car prices and vary a lot by locale and season. The suitability of the floor plan for your needs and the condition are far more important that squeezing the last dollar out of the price.
The Quartzite RV Show advertisement below suggests that this is a one dealer show, so I would not expect any meaningful price competition. It does, however, indicate that both new and used RVs are available.
Paul Evert's RV Country is the "EXCLUSIVE RV DEALER" at The Quartzsite Sports, Vacation & RV Show and will have over 100 new and used RV's diplayed at the show. Check out their website for inventory options and contact information by clicking on the logo below.
http://www.rvcountry.com/
http://www.quartzsitervshow.com/