What I would say as far as pricing goes, if he can get a few of the other band members to pay say 50 bucks for a strap you make, then give him a discount off of that price, I'm not saying 50 is what you should charge, just using a number. I made a shotgun bag for a friend, (clay shooter) and told him the same, if any of his buddies at the range buy one, then depending how many I sell (5 or more) his is free. Unless you don't want to make any more. Or he is the only tuba player in the band. Just my 2 cents.