(1) The test has to be signed by an online doctor. The firm arranges this implicitly, but it's not free. I can't go directly to Quest for any random test I want. The tests offered directly by Quest without an intermediary are too expensive and too few.
(2) States like New York throw a wrench in it by disallowing anyone with an in-state billing address from ordering such tests.
Ideally I should be able to pay the same low rate that the insurance firm would minimally pay, but in practice I can't. I have to pay a lot more if I can get it at all. The cartel is strong.