I think 18% is not high. In my country,Japan tax rate of the profit from stock trading is 20%.
I think these percentages are high in my opinion. Meaning a labourer will spend large portion of his labour gains on just one aspect of his life which is tax, feeding ,shelter plus other life exigencies have not been added. For me, 10% is ok following from at least the biblical guide of giving out 10% of monthly proceed to God's house.