IFR or VFR it doesn't matter, all of GA pays the same for service (in the US). You pay through a fuel tax that you pay each and every time you fill your tanks. There are those who never fly IFR who help pay for some of the IFR services that others use. But then again, they use some of the flight services available. All in all, GA here doesn't pay the lions share of fees, that comes from the passengers who fly the aircarriers, but then again, they are the ones who gain the most out of the ATC system.
regards
Scott