The market is dynamic and your simplistic math is not a basis with which to formulate what a share will be worth.Sure, so redo the math with 5% instead of 50%, the numbers aren't as clean, which is why I did the math with 50% but you should be able to comprehend the point.
A 5% buyback can be executed cleanly if it's done over a period of time and with limit prices and in that case the math works out exactly.
Reducing the float by 5% is not necessarily going to directly translate into a corresponding taxable gain equivalent to a dividend.
Quite often the float still gets bigger as the buyback is not enough to offset the new shares resulting from exercised options.