I've got some Metro style shelves on order as they were on sale, but out of stock at my local big box.
Given that I could probably fit at most 4 carboys across a shelf, I should be good for weight. I estimate a shelf full of bottles would weigh on the order of 250 lbs, so again, good.
On wood: if I had the wood lying around I would have done that (as I did for the other shelves in my garage and pantry), but I figure that I'd end up spending closing to $50 in wood to build an equally strong shelf. The cost may be flipped for other people.