I buy a lot of generic or store brand stuff. Usually I'm comfortable doing this with things that have been around for a long time like bleach, laundry soap, and basic foods. I assume that it is not difficult to do these things so anyone can make it and there's little if any difference between brands.
On this topic: I heard once that you should first buy cheap tools. Use them until they break and then decide what you want to improve about those tools and buy better ones. Often those first tools never break. This seems like pretty good advice for most things.