The only way to have affordable, ubiquitous testing stations is to make it universal. At least, in states that do not also require safety inspections. If only 10,000 cars were tested each year, nobody would buy the equipment.
Mass (low-value) testing is only more affordable if you value people’s time at $0/hr
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.