Oh, argh, shoes. Our elementary-school aged son generally has one pair of reasonably inexpensive (~$40) sneakers that are what he mostly wears, a pair of soccer cleats, a pair of basketball shoes, a pair of decent boots and a pair of water shoes or sandals. And he uses all of them and has opinions about why they matter. Honestly, I've just embraced it -- I'm glad he's active and outdoors, and we can afford them, so I just go with it. Any that don't get worn out before they're outgrown, we donate, but many of them do get worn out (always, the sneakers), which as I say, I embrace as a good sign...
His grandmother often gives him a good pair of boots as a Christmas gift, so at least there's that.