In theory, all three taxes are taxes on consumption. If the tax is 25%, the final cost of products and services would be 25% tax and 75% cost plus profit.
In practice however, the conversion from an income tax to a sales tax would cause 20-25% price inflation (see the footnote on page 144 of "FairTax, the Truth"); because of the embedded taxes in gross salaries. [Since inflation is monetary, the immediate impact would be fewer units purchased.] For those receiving salaries, this would have little effect, but those on fixed incomes would be screwed until the COLA caught up or downward pressure on salaries takes effect.