Hi - I thought I would jump in with just a little bit of information.
I don't have any personal experience with Hercules tires, but understand that Cooper tires are supposed to be of good quality as a rule.
I think that you will find the tire brand issue debate highly emotionally charged and with widely varying opinions - from "I would NEVER put Brand X tires on anything I owned" to "The ONLY tire I ever will trust is Brand X." I guess it is like a lot of things in that people have opinions about what they prefer, but they can get pretty wound up over the tire debate.
The quotes that you give here for rates are very, very similar to what I have found when replacing tires in the past. It pays to know exactly what you want and then shop shop shop. The rates that you quote here are nearly exactly what I have seen.
Personally, I have a strong affinity for Toyo tires; they are well-priced usually and wear extremely well while offering a nice ride...in my experience. The OEM Michelin tires gave a very comfortable ride, but the sidewalls have cracked on 2 different set and required replacing the tires FAR before what should have been their useful life of say 6 to 7 years.
You will find (as in the case of the OEM Michelins) that some sizes are almost proprietary in that you can only purchase maybe one two different brands because no one else offers that exact size. That said, most tire dealerships can give you an equivalent tire that will work fine. Using a different size tire, however will make your speedometer/odometer readings very slightly inaccurate but the differences are generally considered insignificant to a degree that no one really cares. If one wished, they COULD have the speedometer/odometer re-calibrated, but consensus is that the differences are so small that it doesn't make much sense to pay for re-calibration.
Here is some example information of tires that are considered to be 'equivalent':
For an equivalent size, a HIGHER load range tire can always be substituted:
Match inflation pressure to load carrying requirements using load and inflation tables. Some manufacturers use slightly different size designations. Popular RV tire size equivalents:
235/80R22.5 = 245/75R22.5
255/80R22.5 = 265/75R22.5
275/80R22.5 = 295/75R22.5
There are also some other considerations such as membership in clubs such as FMCA which have negotiated discounts for tires with at least 3 different manufacturers. www.fmca.com
and look for membership benefits.
My final comment for you would be to pretty much ignore estimates of how many miles a tire is good for. RV tires almost never wear out, they age out and become unsafe despite having plenty plenty of usable treat remaining. So - a high mileage guarantee is relatively useless to RVers. Not so with truckers, etc., but for our uses many of us go with the least expensive option, knowing that we will have to replace them in 7 years maximum anyway.
Do a little internet research and you will learn more than you ever wanted to know about tires! I hope that this response has perhaps sparked some questions as well as provided a few answers. Best of luck in the tire hunt!