OK, I spoke with several dealers in the area and got quotes from $85 to $130 per tire plus mount/balance.
I then spoke with a good friend who owns a large tire dealership and also is a large/semi/trailer tire remanufacturer. He told me that regardless of brand, I really would NOT see any difference in tire life. He told me that the real determinant of tire life of ST tires are the UV blockers and that there are no differences between any of the brands. In other words, they ALL dry rot the same. If you are looking for tread life, that is a different subject. Since my trailer mostly sits and probably only gets used for 500 miles a year, I went with the cheaper brand. I just had 5 D-stone tires mounted and balanced for $525 yesterday.