What up with that? Part 1

So there are like 50 different types of steel/aluminum/not plastic bottles on the market and I can't figure out what the difference is (ok, I haven't tried soooo hard). Why are some $25 each and others $6.99? Why can't they make a good sip-nipple or whatever that's called? I either end up with water dribbled down my front or too much air in my stomach and then the burping begins. I'll pay more if there is some advantage but otherwise I just feel like I'm getting ripped off.