I do mostly tennis court cleaning,
What surface are they?
If they are porous macadam (most likely) I clean them with fsc then jet rinse, I would charge from £375 (up to £750) for a single, on blocks of three more from about £300, depends on condition of courts, water supply, location etc.
Allow at least a day per court when pricing.
If its an acrylic you will have to be more careful as they can need recolouring and synthetics are a no-no with pressure washing.
Any pics?
Cliff