heres what i figure.
material costs for one set: 20 dollars
for a 1'x1'x1/2" piece of aluminum its roughly 60 bucks and you can get about 16 plates of that much material. 1x2 is 100 dollars and so on. the bigger piece of aluminum you get the cheaper the cost.
designing and programming
50 bucks as it is a simple design and simply takes minutes
bit wear and replacement
? as i do not know tooling but i would imagine pretty cheap as they use one bit for quite a while.
profit. alot seeing as they wanted to charge me 71 dollars for each piece and wouldnt budge when i told them that i knew how much it cost for the material. he tried teling me it cost 60 dollars for one piece of aluminum lol