People don't reload strictly for the price savings as your post alludes to. I do it for the hobby and to try out some funky loads.
I reload because I just flat out like to do it. I have been reloading since I was a young man and I started because of cost but kept doing it because I like it:)
So do I - for getting precision rounds in 300 Winmag for my target rifle. But I'm afraid your point is somewhat off - for a SMG the reloading pertains not to quality but to quantity and thus to the monetary side pure and simple. [How to get several hundred rounds, hopefully without duds, and not to incur too much of an expense]. To reload on that scale one would need an electrically driven reloading press - and these are $$$ themselves.
and squeeeeze out every last drop of variable to accuracy.