We live in SoCal and use a cover. We use a mid grade cover - about $300 range - and change the cover every 3-4 years when the Tyvek starts to shred/disintegrate. Plus the cover gets a bit soiled from constant dirt/dust blowing in the wind and cleaning a cover that big is problematic.
Here is what we found in our research:
Camping World prices can essily be beat by searching on-line for the exact type...and other brands. Just be sure to avoid the "Universal" covers. They are poorly made, will flap in any wind, and can 3asily blow off the RV.