I see simpletire has free shipping. What is the cost at TireRack with shipping?
Using heeni's display address, it's about ~$16.70 per tire more. So ~$54 less total before ST rebate at TR even with shipping. And TR currently has a $70 TR rebate on Michelin Tires.
Using the same example Tires-easy .com has the same Michelin tire with free shipping no rebate ~$452, ~$60 a set less than ST with the Amazon rebate. https://www.tires-easy.com/225-60-18/michelin-tires/primacy-mxm4/tirecode/99702
With DTD/DT BF promotions coming soon, no $500 limitation, the $50 ST Amazon card will likely be even more insignificant.