It also depends on your accountant and personal circumstances. If you are married (unlikely in a junior FO) Irish tax arrangements are far more advantageous (you stay on the lower rate for an extra €9000). How you choose to manage your expenses also depends - the smart way is to pay yourself a salary up to the top of the lower tax band and then take the rest in expenses, but many take farcically low salaries and burn through their expenses.
Tax compliance helps you sleep at night. Remember, the taxman can go up to at least 7 years back depending on jurisdiction. Consider how you might service the flying training loan you may or may not have. I would say €3500 average is reasonable depending on where you pay your social contributions. That is the biggest issue on newer contracting models as in some countries they border on larcenous and the EU require you to pay them where you are based,not where you may actually live.