I don't buy a particular item just because it's the most expensive. None of my gear is the most expensive. Had I bought the most expensive of everything, my BOB would have cost me $10,000 instead of $4,000.
I search the web for reviews, and I come to websites like this one and ask other people what they think about a product before I go out and buy it. For example, before I bought my water filter I searched google to get a variety of opinions. Then I posted questions on several different forums, including this one, asking for input. The general consensus was that I should get either a Katadyn Pocket or a Katadyn Combi. The Combi is the cheaper of the two, and that's the one I bought, but it still cost me $100.