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theory/strategy for pricing by volume
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actually, the rate of change could be more or less constant, but you might have a minimum price that represents your fixed costs.  so you might sell a milligram for $1 (which is ridiculous in terms of per-unit pricing) to cover fixed costs, and add $0.50/lb for each step in size to cover variable costs (cost of raw materials and packaging), so a 2lb bag would be $2, a 5lb bag would be $3.50, a ton would be $1,001, etc.  at the end of the day, you want the marginal revenue (the price that you charge for each additional pound) to be more than the marginal cost (the price per pound it takes to produce the bag).  any amount over that goes towards your fixed costs - the cost you'd incur if you sold zero product (rent, utilities, overhead, etc.) it's not an exact science, and there are many variables that go into pricing.
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