It probably is not worth the trouble to make if you are making all of the slots 3" on center like the manufactured slatwall. However, I remember a friend of mine complaining about the cost of it when he was opening a retail store awhile back. He only used four or five "rows" from the slots all around his store. With the metal inserts costing so much, that was a lot of unused money hanging on the walls.
That Outwater place also charges a $30 pallet fee, plus the shipping charges. I don't have a point of reference for truck freight for something heavy and 8'x4', but I do know that it would be much cheaper to ship something that weighs 200# and fits on a single pallet vertically. The total weight of my Kamado ceramic grill shipment was 630#, but it was well contained so overnight truck freight from Sacramento to my Las Vegas backyard was only $146.
I don't know how much our local cost for the stuff is.