I don't see what the issue is. Pay the people running the test station more per test but less overall.

Extremely rough example numbers: Instead of testing a million cars for $20 each, 10k cars are tested for $200 each. 85% of testing stations shut down, and the rest downsize if they can, but there's still plenty of them around. The total cost of testing drops 90%. The state taxes every car $2 to pay for the randomized testing; being selected means you lose an hour driving to the station, not that you lose $200 of your own money.