I don't think that it's all instantaneous. I think it also takes into account that high taxes stifle growth.
High taxes don't necessarily stifle growth. Although taxes in the US has been cut since Reagan, there has been no growth in real wages for Americans who are not part of the financial high clergy since the 70's. Real wages has been stagnant or dropping.
Another necessary consideration when talking about growth is that of ecology. Insisting on unlimited growth on a limited planet is a prescription for disaster.
Well it's hard to say. Has Sweden ever tried anything below 50%?
Of course Sweden has had taxes lower than that in the past. I don't know Swedish tax history that well but its neighbour country Denmark is comparable. When the income tax was introduced in 1903 a tax reform the highest tax bracket was 2,5 %. Back then the opulent were furious and claimed that these outrageously high taxes would stop all growth and bring the country to the poor house. Similar arguments were made when the tax rate was raised to 5 % in 1912 and for every subsequent rise in taxes ever since. Every time the wealthy predicted economic disaster.
The same thing happened for all social programs. When public schooling was introduced in the early 1800's the farmers who had to pay to build schools and would have to do without as much child labour as they were used to predicted that the economy would be devastated. All subsequent social programs for education, health care, unemployment insurance and pensions were criticised by the opulent for being way too expensive and far beyond what the economy could sustain. Also arguments were made that this public help would make the unwashed masses lazy and unwilling to work.
All these dire warnings proved to be untrue. Back in 1903 Denmark was effectively a third world country with a small class of extremely rich land owners who controlled society. The mass of people were utterly poor, children were malnourished and families were cramped together in small, cold and unhealthy abodes.
Then came the "economic disaster" of higher taxes and social welfare programs and these helped to gradually transform Denmark into one of the worlds richest, safest, happiest, least corrupt and most innovative countries. The economic disaster for the rich proved to be an economic miracle for the nation as a whole.
And what do libertarians offer today? They offer to take our respective countries a hundred years back in time to be ruled by the iron fist of laissez-faire capitalism. They offer to create the same legal and economic conditions that once has proven to result in mass poverty, hazardous work environments, child labour, pollution and massive social divides.
Libertarianism was tried once and it failed utterly for those who were not lucky enough to belong to the class of owners. Why would anyone in their right mind want to repeat this mistake?