Well, Quartzsite is a good spot for solar stuff, they have competing stores within scooter distance
However if you want the lowest beyond a doubt price consider this.....
Several state and county road comissions are now using solar powered arrow signs and changable message signs as well as other devices along our highway (including some cameras and relays believe it or not) now as this equipment ages it is often sold at auction. It is not usually the solar panel that is "old" but the batteries or some other stuff,,, Or it may be that it got "Smucked" tearing up the electrincs but again, the panels may well have survived.
You can often pick up some "Junk" for a five or 10 bucks, strip off the panels, which are in perfect condition and sell the remaining metal for what (if not more) than you paid for the pile at the local recycler
Now that, is cheap
All you got to do is find out when the county auction is