I was also noticed the belts from Cat were pretty costly.
Regarding the Dayco belt, I have been running that same belt on a XF 7000 for the last 2,000 to 3,000 miles without any issues. In fact, I am replacing the belt with another one like it because of the prices and my past experience with the belt. I am not replacing the belt because it is bad, I am in the habit of replacing belts after a few thousand miles. Keeping the old belt as a spare. Just follow Cat's belt break-in and it will be fine. (No, I was not taking easy on the belt either. Many trail miles of grapping a handful of throttle with a 141" x 2.25" track.)