Shooting, be it airsoft, paintball, pellets, or real steel consumes ammo, which in turn consumes money. I too am a pretty avid basement shooter, and I accept my ammo costs as part of my activity. You can either afford to do it, of you can't. In the end, all decent BBs will end up costing you about the same amount of money, regardless what brand you get.
Personally, my choice of ammo is BB Bastard and Metal Tech. Both are pretty reasonably priced IMO, even when you compare them to "cheap" .12g crap you get at Cdn Tire. You get quality .2g BBs for about the same price.