If Apple's fees cost 30% of the price, then the actual developers who make the software must raise prices to make up for Apple's fees. How much, though?

One might intuitively guess 30%, bringing $1 to $1.30. But Apple will take a cut of this price increase as well: $1.30 * 70% = $0.91, so still losing money to Apple's fees.

The actual amount they must raise the prices is (1 - (1 / 0.7)) = 0.428, or roughly 43%.

Doing this math backwards to factor out Apple's fees yields a confirmation: $1.43 * 70% ≈ $1