All LARS both civil and military is funded by NATS En-Route Ltd., who in turn get their funding from Eurocontrol Route Charges. The budget is quite small and the payments to individual airfields vary depending on hours/days of operation ie those providing it 24/7 get more than those providing it mon-fri 9-5 to quote the two extremes.
Edit to add:
No way does LARS funding pay for any extra staff, the intention being LARS is provided from spare capacity at radar equipped airfields, apart from the Farnborough operated London LARS system which is subsidised from NATS own budget
Don't forget it's all free to the end users though.
Last edited by chevvron; 6th Aug 2012 at 08:30.