For one-offs, it's not cheap... More than $100 or starters will get you a fairly small aluminum part... $150-$200 gets you more thicker slab of aluminum to work with. Price doesn't rise much from 1 piece to 100 (if the parts are small), so best economics are to manufacture a bunch of whatever it is at once. With CNC programming apparently there is a lot of work in the set-up, and making duplicated pieces after you've got the first one already made is relatively cheap.