If they make use of Galileo mandatory for (say) airlines and ships, collection of fees should be simple.
There has been a lot of recent discussion about funding Galileo since the work will be parceled out to EU countries based on their financial contribution to the project. A funding drop-dead date was recently succesfully passed.
To some extent I consider Galileo to be an "electronic Airbus", taking benefit from being 20 years newer than GPS. But GPS hasn't been standing still during those years, what with fielding WAAS, etc.
One obvious reason for Galileo is the ingrained fear that the US will turn civilian GPS off or reintroduce SA, since GPS is run by the US DoD. It is a case of distrust of the US commitments to keep the non-military part of GPS on the air and keep SA turned off.