Craig's list or ebay has bargains on them from time to time.
If you are in the Phoenix area, there is a tire 7 rim on craigslist.com
RV/Motorhome Tire& Rim 235/80R22.5
You could also look into other brands, but they will only be $50-$100 less than the Michelin. Try Toyo or Continental or Bridgestone.