As you probably suspect, they're not the high-end proteins. Whey is digested much faster and is generally considered a better protein, but personally I think it depends on the context. Whey IS best if you want to get a LOT of protein into your system FAST, but if you aren't going to be able to eat for a while, a slow-digesting protein like Casein would be a better choice, like at bedtime.
Personally, I think a cheap protein is fine as long as you like it, and as long as it doesn't upset your stomach. If you've got a huge amount of muscle mass you need to maintain, it might be different, but face it, most of us don't