Is it possible they are trying to sell for the same price but with wildly varying costs of each varietal of coffee? I.E. they want to sell a bag for 15 bucks across the board but some beans cost them far more than others to source?
It's on us though. They're lying to us to get our money, our labor, our consent. We let them.
Why?
The varying of quantities in the same sized container is not the problem and is certainly not illogical. The problem is when we allow marketing departments to lie/cheat/fool the product onto a different portion of the demand curve instead of letting the $/amount naturally flow back when price decreases or when it makes sense to switch to cheaper containers.