"Business income taxes of 90% would not affect pricing decisions other than accomodating elasticities. If you believed you had to increase your price to account for the tax you might conclude that there was no way you could increase your price that much because the elasticity of demand is such that it would cause your sales to drop drastically thus it could mean you would LOWER the price to prevent demand from falling too much."
Business taxes suddenly going up to the 90% level would typically mean that previously profitable businesses would now be unprofitable, all other things considered. If the taxes affected all businesses in a given market equally, then those businesses would attempt to increase their prices to pass those costs along and remain at least marginally profitable. If the market would not bear that price increase, then these unprofitable companies would go out of business.
This was an extreme example, of course, but it would not mean that companies would become unprofitable. They just would not be able to keep as much of their profit but would still be profitable.
Our rate were at that level for some incomes but the economy still lead the world.