I have a set of R250's to put on my new fifth wheel trailer. It's hard to believe that the LT (E) rating on the tire is the same as the Toyo Open Country A/T's on my tow truck. They're substantially thicker and so much heavier. Costco had a $70 Bridgestone rebate which brought the R250's down to $195 each--a great price.
The manager at Costco said they order R250's in for 1 ton trucks with utility beds and other very heavy applications, like service trucks with welders and cranes. He said they're not a truck commonly put on personal use pickup trucks--too beefy. They suggest R500's for daily drivers that need such heavy duty tires.