Earlier quoted context omitted.
Hint: At the point at which they agreed to sell 6000 units, they must've agreed to a price for those units. Then later they figured out that the trader meant cases and upped the number. I'm thinking they expected to get paid about 6 times more (6 packs per case) ...
That's not the way I read it. Like you said, they must have agreed a per unit price. The mistake had to have been purely in volume. When they recognised the mixup with cases / bags, they wouldn't have pushed to deliver the actual expected volume had the unit pricing been a problem.
As someone that has gone through the process of trying go to build a business that sells to distributors, I cannot understand how you’d miss a 6x discrepancy in your price model. Your margins are slim, a 6x markup means you’re seeing more than 500% profit margin. (Probably by not having a price model, if I had to guess…)