$750 for a set of ST tires? THAT'S EXTREMELY HIGH!
On the chart posted, it is missing Carlisle HD's, very much an equal to the Endurance.
And there is still no confirmed proof from Maxis their ST option is Q server/speed rated. Such information is only found on reseller web sites. It would be nice if someone could post an image of their sidewall to confirm the Q service code.
Also, an inaccurate statement posted on the chart. The ST "spec" per tire load/inflation charts and federal regulations does NOT override the manufacture.
The manufacture sets the speed rating of their product and what's on the side of the tire is the speed and max cold pressure rating. Period. No exceptions.