The FDA just approved the first commercial antigen test for COVID-19.
This is not an antibody test. Antibody tests look for antibodies that provide immunity as a result of previous infection. Antibody tests return negative if you've never been infected, or are in the first 2-3 weeks after infection...or if the infection was long enough in the past that you no longer have antibodies.
PCR tests check for RNA from the virus in a current infection. The chemical processing doubles the amount of RNA over and over, making them slow, expensive and very, very accurate. They can be so sensitive that they can show positive very early in the infection, and even after the infection is cleared if traces of viral RNA remain in your system. These are the main tests used, and have been subject to backlogs of over a week for processing.
Antigen tests look for viral components, the same things your immune system responds to. Because they don't chemically amplify like PCR tests do, they're cheaper, faster...and not nearly as sensitive. If you're in the early or late stages of infection, they'll probably give a negative result. But if you're in the contagious phase with a heavy viral load, they'll usually catch it.
Pricing on this test may be as low as $5 in huge volumes. It will be useful for routine and repeated screening. It's a simple nasal swab (like a flu check), not the brain-stabber that most PCR tests still use.
This is a big step forward, but there's another leap coming soon. Those are saliva-based tests that are on the order of $1. That's the screening test they should use every Monday morning to test every student and staff member in schools. I expect some of these to be approved in the next month or so.