You are wrong. The 23% is the percentage of the GROSS (after-tax) price, not the base price. In terms of the base price it is 30%.
If the gross price is $130, the BP is $100 since 23% of $130 is $30. Hence the gross price is 1.3*BP.
I know it's weird, but that's the way the FT is.
Lets just put away the numbers for a moment. Basically you guys are saying that Sellers factor in the taxes. Well nothing could be further from the truth. You see Sellers will not be taxed. Only the buyers on a volunteer basis. Not like the way the current progressive tax, and or the flat tax.