I did a little research into the guns, but not ammo costs. I figured .45 would be a little more expensive but not .44mag-expensive. It's still not that bad. Especially considering everything that goes with an SAA...manual hammer cocking. Individual loading and extraction. Just plain heavy and, though I like the way they feel in the hand (of course), not very ergonomic.
So rounds go a hell of a lot slower than they would through any of my 9mm automatics. If you compare an SAA-style revolver to a 'wonder nine,' I think I would confidently call the former much cheaper to shoot when price your ammo against the time it takes to fire it. Rather than simply cost per round.
Going to a Ruger and shooting .38 would be much cheaper, but I think the combo of .38 plus a gun that's not as intentionally archaic* would simply make me not want to shoot it as much, so the purpose could be self-defeating.
*As roughly stated above, I can confirm that the action of the Ruger feels more modern. For that matter, a new El Patron (the top-end of Uberti's normal SAA's; ~550-600 bucks new I think) also has a lighter mainspring and what feels like a generally more polished action resulting in a loss of 'character.' But the gun itself is heavier and more traditional-feeling than comparable Vanquero. Actually, though, the grips have been slimmed and modified in a subtle way that makes the gun feel VASTLY better than a 'base model.' Better than any of the Ruger grips. I'd like to keep the Uberti I bought, as it's a good basic 'first' for the type. But I may well consider the El Patron over a Ruger if they sell it in .357 (think so).
edit: Oh, and the El Patron has a big flattened hammer spur. Lots of purchase and all very rounded edges. It's a very nice touch that I feel would make me practice hammer-fanning until I broke the damn gun.