I have a MEC SizeMaster with 12ga and 10ga dies. I think I ran the numbers on target loads, and if you included the cost of hulls, it ended up costing MORE than just buying cases when they went on sale.
Then I tried running numbers on hunting loads, and those didn't really seem much cheaper either.
The conclusion I came to for 12 ga was that it wasn't worth getting into for saving money. If you're using a more niche caliber (say 28ga or .410) then yeah you can definitely save some cash.
I do think there's value in having it even for 12ga if you're looking to do an uncommonly found or unavailable loading. Say, #1 bismuth for waterfowl, or some crazy TSS loads for turkey hunting (though a few companies now offer TSS loads). As with a rifle, it is there if you want to find the best performing load for your gun.
For me, I kept my press for that reason, and for the fact that I think 10ga is going away.
Not sure how familiar you are with shotgun reloading, but to me, the biggest thing that stuck out is how particular a load is. When I'm reloading for my handguns, I can use almost whatever brand case I want with whatever primer brand, so long as I keep OAL, powder and bullet the same. NOT SO with shotgun. Shotgun loads are very particular as to which hull, wad, primer, and (of course) powder is used. Steel also uses different charge bars, though it seems like the general consensus is that steel and steel powder flow and meter so poorly that it's just better to do so by hand.