That's one reason to make your own reloads. That, and it's fun.
Cheaper 9 mm is about 11-12 cents a shot. Reloading would be about 6-7 cents in components + time. Even on progressive manual press one could do maybe 300 rounds an hour [sustained rate]. Thus one would be saving about $15/hour by reloading 9mm for a SMG. More, that guy I mentioned would be spending an hour and a half just to reload enough ammo for his 10-15 min session.