Can someone please tell me if this is a good deal or is it sketchy?

That’s a pretty “cheap” bike for a bike shop, and the story is pretty normal. Bikes, like cars, depreciate immediately, so 20% off is really not that much. You should be paying some sort of discount given you don’t have a shop backing the purchase up now, even though it’s basically still a new bike. If you are really concerned, ask them for the sales paperwork when you take a look at it. There’s no reason they wouldn’t have it still if they’re legit.