My office did M21 and told me that if insurance didn't cover it, I'd only have to pay about $200ish. It went back and forth between insurance and the testing company for a while and in the end insurance sent me a check for almost $1000 for it. The testing company had me sign that over to them and I didn't have to pay anymore. Although they still tried to send me a bill and I had to call about 3 times to get it cleared up. But I was happy to not have to pay.
Oh and I decided not to find out what we were having.