I don't think deduction means what you think it means. If you deduct 100%, you aren't deducting it from the total tax owed. You are deducting from your total taxable income.

So if your tax rate is 30% and you spent $1,000 on a camera, you will save $300 on taxes. So the camera is not free. But you do get it for effectively $700.

Additionally, you can't deduct the value of a purchase AND depreciate it every year. You do one or the other. And which one you do is dictated by tax law.

Double dipping is tax fraud.