Except you example is not relevant, as the our tax rates are bracketized, meaning that the initial $49,999 is taxed the same rate in either scenario. The higher marginal tax rate would be on any any additional income earned in the higher brackets.
I'm a Libertarian too, so I'm not arguing necessarily for a higher tax rate on higher incomes. But I am compelled to correct disinformation.
You are correct about marginal tax rates and how they work.
However, you are forgetting that one has to work just as much if not more to cross the bracket.
The Doctor referenced earlier cut back his practice to 3.5 days. Why? He made a rational economic decision.
If he works 3.5 days to take home say $2000 after taxes he takes home $571 per day. If he works 5 days and as an example now takes home after taxes $3000 he is now earning $600 per day. So he had to work and extra day and a half to take home an additional $145 ($29/day for 5 days). Depending on how he values his time and effort determines the decision he makes re: working more.
Does that happen. Yes it does especially to those that are riding the line close to earnings that put them in the next higher bracket. It happened to my father more than once in the 80's and got to a point where he told his employer to not give him a raise again until it would be large enough that he would actually take home more instead of less due to the raise. He was a very high income earner and ended up taking a raise about every third year.
You may want to look into economic indifference theory for an explanation of the choices consumers make for a more detailed explanation as to why one would accept less income to get more free time and less work.
Its a complicated subject and is one of the most fundamental foundations of economics.