I have described how profit is a residual and it is on this residual that income taxes are calculated. Income taxes do not enter into the calculations determining the cost of the product. However, the costs of determining the profit and income taxes ARE true costs as they are there whether there is a tax paid on not.
Prices are determined by market conditions thus one can never know whether there will be a profit or not. If the market does not allow a price high enough for a profit then there is no tax. Hence it is not a "cost" as are the components of the product which have been paid.
By your logic income tax would be a cost if there is a profit but NOT a cost if there is none. Hence it cannot be compared to a true cost which is a cost in either case.
By my real world experience, income taxes make me charge more than I would without it. Is that in opposition to your position?
If you don't pay income tax, is it a cost?
Beyond that li'l gem, there are costs that business pays even if their income tax liability is zero.