You would never pay "away all your money towards taxes" - and contrary to popular belief, we have lower taxes now than we had for most of the 20th century.
It always pays you to make more money, you always retain most of it. Except in the case of tax credits, spending money just to write it off costs you money - since it only reduces your taxable income dollar for dollar but not taxes are only reduced to a lesser amount according to your effective tax rate.
What the write-off does is exclude your business expenses fro your taxable income.