Depending on your contract I would say 80% is possible. As a contractor you will be able to take all of your expenses from the top before tax. If you are on a floating contract that would allow you to take out all the travelling costs, hotel and food costs. Then there is your normal training, uniform and equipment costs to deduct. Even if you are on a based contract, you will still be out of base quite a lot and the above will all apply. I would still recommend you get a Ryanair employment contract if you can.
Less money perhaps but a lot more security.