For the curious, I wanted 3d6 +/- modifiers, giving a bell curve with a range of 3-18 and an average of 10.5 at zero modifiers. I knew rolling three dice might get too complex to do on a large scale, but I wasn't counting on not actually realizing where I'd go from there. Also it might need multiplicative modifiers rather than additive ones to avoid getting -6 as a result or needing +40 in modifiers to produce a masterpiece.
EDIT: I didn't explain this well, and maybe it's more salvageable than I thought, if we're willing to roll three dice, add the results, and multiply them.
Anyway, think of it like this for the moment: Your result is the value of the item, so 10 is an Item, 20 is an -Item-, etc. I'm not sure what a 15 would be, but that's just a display issue at that point. So, maybe an unskilled worker has a modifier of *0.5, so they usually produce 5 quality items (10*0.5), and can only make 9 quality at the very best (18*0.5). A decently skilled, equipped dwarf, on the other hand, has a modifier of *1, so they produce normal items most of the time. A skilled dwarf might be *2, so they can produce 36 value items if they get very lucky, or 6 quality items if they mess up, but normally produce 20 value items. In between, you could have *1.7 or whatever the particular combination of skill, tools, and such requires. Still complicated, but makes decent sense and mostly does what I want it to.
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So yeah, maybe it's salvageable, maybe not, I'll have to think more about it. Maybe some sort of crit system would be better for achieving rare effects, like 1d10 and reroll and add it up if you get an 8 or higher, or something. Or maybe item value could use triangle numbers, so a +1 item needs a (modified?) result of 1, a +2 needs 3 (1+2), a +3 needs 6 (1+2+3), etc?