Heya, checked out the manufacturing costs for big rocks, and it seems like the benefits of processing them are too small. Checked out the ruleset and did some math, and you statistically get under 2,000 credits in the 400 workshop time.
When you check out the equivalent gains for x-grog in that time (~8000), you essentially gain -6000 by processing them. In other words, the huge fee for selling each rock (5k each) is cheaper than processing them.
Since you eventually will end up selling them months later, it's kinda like starting the game off with -850,000 funds. Yikes.
I'm assuming they were mainly added to stop you from selling your armored vaults in january, so I'd have hoped they would add some value rather than just be a pain in the butt. Lowering the rock production from 775 to 100 (so 100 {}, 50 ore, 35 corpses, 10 silver, 10 gold, 1 of each gem) would at least put it in line with x-grog production. That would yield on average ~4 gems, so this makes it a very random treasure chest with an extremely long processing time. So they're still an annoyance, but at least you get some shinies out of it rather than just paying some dudes to ship them out of your base.