I'm trying to decide which full-size Glock to get, the 10mm G20 or the .45 G21.  I'm not concerned about the difference in recoil, but I'm curious about the cost of ammo.  Is there any cheap practice ammo in 10mm for the same price as 45?  

The most common 10mm ammo in my area is the Remington/UMC 180gr FMJ's in the nickle cases for $15-$17 per box.

The cheapest I've ever seen is the CCI 200gr FMJ Blazers for $10 a box.  I've also had good luck with reloads from Georgia Arms if you want to buy in bulk.

I've been shooting the 10mm since about 1995 and ammo has run just slightly over what .45 ACP costs.  You may have to look around to find it but I don't think it's that much more expensive.

I'll qualify everything I've said though since I haven't bought factory ammo since I got into reloading two years ago.

Forget about getting ammo at the same price as .45acp, it isn't gonna happen. You can get close, but not quite.

Have you thought about the Glock 31? I just bought a 32 & LOVE the caliber!

My personal vote would be the G20 ...I'm very fond of the 10mm.

Check here for ammo:
www.ammoman.com/webstore_10mm.htm

The Federal 180gr is pretty cheap, and the bulk Hydrashoks are the best price I've ever seen on them.