I'm not sure it is the first time it's happened, but it may well be the first time that any airport has been so up front about it.
Usually, you will pay these sort of fees as part of your ticket price and be none the wiser unless you take the trouble to break down the prices.
Personally I congratulate authorities for their honesty, why should the council tax payers have to subsidise the airport operation any further?
Even for a "low cost" operation, £5 is nothing, especially when the only option is a very long and expensive train jouney, or a very long car/bus ride.