Best formula for price depending on amount What is the best formula of price of the product depending on amount. I mean "best" in psychological, marketing, stock rotation, profit maximizing, etc sense (any of them or all together, if possible).

Say, I often see that prices on Coca Cola bottles growing not as fast as volume of them.

I sure there is the best formula, invented by psychologists or derived empirically then proved in use.
I think your expectation that a "best" formula exists is very unreasonable.

There is no "best" car design, there isn't a formula to design the fastest airplane with total weight $x$ and there is no easy formula that will give you the best price in general situations.

Sciences have a lot of unsolved optimization problems. Economics, psychology and most sciences involving humans have a lot of seemingly unknown variables, further complicating things. So while there are some principles which you can base your pricing strategy on I have never heard any reasonable person claim that a general best price mechanism exists and I don't think it does.