If I were buying a bike in that price range, I would take a really hard look at this before Costco. One huge advantage that was mentioned is, it will be tuned perfectly when you buy it and it will be properly sized for you.
https://unitedsport.ca/collections/b...020-trek-black
These bikes come sized. If you are tall or short, you can often get a great deal on last years model....... yes bike snobs will pay more for this year's model.
EDIT: From the Costco pic, I really don't like the look of the tires. I would prefer smooth rolling and little resistance over a bit of cushion.
I would take good caliper brakes over lower end disc brakes any day. Much easier to adjust, and I suspect cheap disc brakes are really hard to adjust, which you do annually.