So I'm not sure if this is a useful response to your question but I recently did my own pricing investigation. I've built copper vessels in the past so I would have been fairly comfortable attempting the same in stainless. This is what I ended up concluding from my research.
For kegs the cheapest guaranteed legit source I found was:
The Vintner's Vault at $80 + S&H ($44 / keg estimate to Rochester, NY - so $124 shipped - probably a bit more to you).
For pots just about the best I could find was the 62 quart stainless steel
Bayou Classic 1060 on Amazon (it was free shipping w/ Prime) - so $120 shipped.
I couldn't find a source for stainless steel sheet metal in the appropriate size and thickness for significantly less than these two options. I didn't hunt too hard because if I did find a source I'd also need some extra stainless, a welder, and time invested in learning how to use it will (or pay someone to do the welding for me). I have friends that weld but none that do stainless.
I hunted around a bit for various other container options and didn't find anything of similar size for a similar price. One issue I ran into when doing pricing was that when you get into less-frequently traveled containers the costs for false bottoms seems to go up drastically if you can find something at all (if you can source the raw materials for cheap enough then maybe that's not a concern).
If you went aluminum you could reduce those costs.
I have access to large kilns and plenty of ceramic working tools so I considered building some giant clay pots to use (I'm planning on going all electric).
The best way I could figure would be to make some flat port areas into the pots that could be secured with nuts/bolts/washers similar to a weldless kit. After figuring the costs of materials to custom build the fittings like that & not knowing 100% for sure that it'd work combined with the fragility of ceramics I figured I would be better off with a metal-based option.
I also couldn't easily decide on a good false bottom solution for the giant clay pots approach
.
I ended up going with used stuff off Craigslist because it was by far the least expensive option and the guy said he'd acquired them legit (with the amount of money he said he had into them it lines up with the price of used kegs shipped to the region off vintner's vault).
As to some other random ideas - it depends on what you can find. If you can source some old stainless milk jugs, for example, they might do the trick.
Good luck with the hunt! Curious to know what you end up with.
