Light bills are based upon a rate which is known before hand as are copier costs. Though I know you don't like it they are easily calculated because you know all the variables in the equation. You know the amounts the rates are applied to thus the total bill.
You do not know if there is a profit until the accountants do their work at the end of the year thus you do not know the income tax. However, that has not had the slightest effect on the determination of the price of a product as have all other costs.
It is not sales revenue which determines whether a profit is earned or tax owed. One must have the cost picture completed before profit, a residual, is known. Let's say you owe no I.T. on sales of 1 billion then the next year sales double to 2 billion. You still cannot say whether there is any profit or tax just from that information. (Although I never said that I.T. "cannot be paid with sales revenue" in any case.)
Income taxes are based on rates which are known before hand too.
That's not right. You don't know the amount of usage. Also, in some places, the kwh usage changes depending on usage level. So besides not knowing the value to use for the variables, you don't know which variables will be used in the calculation of your light bill.
How is it again that the light bill is an expense paid from sales revenue, but income taxes aren't paid from sales revenue? BTW, if the money to pay for income taxes doesn't come from sales revenue, where does it come from? Of course profits come from sales revenue too.
I cannot definitively state the value of division by zero either. Neither has anything to do with the fact that income taxes force my prices higher.