For the short loops (10 – 12 inch loops) I like the bodbands and Phantom Fit bands. They come in sets (5 and 4 respectively) for around $10 – $12. They are a slightly thicker band and are kind of finished on the edges. I have not broken one yet, but I don’t use them as much as I use tubing when it comes to elastic resistance.
These are also great bands, and the education component is great. Dave “the band man” was one of the original rubber band educators and is a physical therapist. I’ve got several sets of these bands, too.
What I tend to do is wait until I need bands and then see what is the cheapest for my current need.