Since there is no cap on "incluse tax" the correct answer to your specific question is 'nothing'. 50% TRUE tax=100% "inclusive tax", and 100%=infinity. Whatever a 10,000% tax would be is in there somewhere.
Nope, I got it backwards, whatever a 100% TRUE tax would be on any item would be equal to a 50% "inclusive tax" on the same item. Nuts.