I looked into building one myself and priced it out. The one from AHS is slightly more but is put together for you, the "arm" is bent to the correct angle and it is cleaner than I could have done it. You just drill a hole and attach the thing. 20+ batches on it and no complaints.
It works great, I put 10 gallon batches in it and there is a ton of room left, I dont know if it will hold a full 15 though.
There is a guy that has then names Doug but he hasnt been answering emails lately. I think I was paying $22 delivered for them. I also use them for bulk grain storage.