there is NO reason other Companies have to sell theirs for so much. I LOVE my Evanix Rainstorm One magazines. The generation two magazines are so expensive. The One's have NOTHING to break. Maybe change 2 O-rings every year or two with no disassembly at all. Spring actuated magazines can jam, bind, kink, wear out. Never happens with The Rainstorm One magazines that cost under 20 bucks.
I personally have 2 Rainstorm II magazines; but if they ever break or are lost I will use the single shot trays I'm looking to have made or buy somewhere. If it's not semi or full auto, I don't see the point anyway.