Go to autozone order over 125$ get 20% off that order. I ended up paying right around $70 a belt last year. Autozone has good deals on belts delivered to your house or store.
I have found my gates haven't lasted as long as the stock belts, but since they have a warranty it doesn't matter to me. One thing to consider is that they usually drop rpm 100-200, so for me at least it brought rpm pretty much dead on with what I was shooting for, and on my sled it held RPM better with the gates than with stock belts.