We have two sets of wheels, so that Costco price is for tires only, but is still an awesome price for WS-70 Blizzaks.
On the Corolla, there is no way for the owner to have the TPMS read a second set of sensors, so if you buy a second set, you have to visit the dealer twice a year to enter them. F-that. We live with the light on in the winter, no biggie.
We bought steels through TireTrends originally, but I don't think the OE steels are very expensive. I just hate the idea of giving our dealer's service department even $1 of my money.