I figured this will benefit some who still use a lot of postage stamps. Stamp prices went up to 58 cents at the end of August, but Costco is still selling them at the old rate (a hair below 55 cents a stamp). These are 'Forever' stamps so you can use them regardless of future rate hikes.
This shouldn't be YMMV as there was printed signs at the register advertising the fact. My location has holiday stamps available now as well.