Labcorp is one of several labs and most hospitals have their own labs and only send out specialized tests.
It is true - you can’t test every patient for everything. There is an estimated 1B primary care visits in the US each year. Assume every patient get 5 tests at $50 a test and you just spent a quarter of a trillion just on tests.
The test itself for lyme must be inexpensive - The vet did a test for my dog as part of routine yearly office visit. I don't know if it's just in my area, or if it's common now.
Looks like Labcorp made over 3 billion dollars last year, so I think probably that number would go up instead of collapsing?