A buddy of mine used to be the shop manager for a company that made cryogenic vessels. They built one for SpaceX that was a 304SS 60" diameter vessel and had a 9" wall thickness. It took them over a year to get the shell and heads. When the heads came in, they didn't meet the minimum thickness, so they had to map the head and then do an overlay for the thin spots.
I forget the exact number, but he said it took something like 1200lbs (I might be mistaken, and it was 2200lbs.) of filler metal to just weld one of the heads on. All done with MIG because it needed to meet hardness testing. You'd essentially weld a bead, then grind/clean it, before welding the next. It took them almost a year to build the vessel, after the material arrived.