As ScottW says, the Red Cross does not charge. We were in the same time frame as you, a Friday departure, and so we took our test on Tuesday. The nice people at the Red Cross were concerned that we were too early, ( i think they thought the US test had to be within 3 days of the flight- meaning Wed, not more than 3 days before - which is Tuesday ) but they agreed to do the test anyway, and it was accepted at the airport no problem - though I did have to point out to the agent where it said the results of the tests and type of test . BTW, we were very impressed with how accommodating they were and we asked if we could donate anything and they said they do not collect money at the site, though you can use the Red Cross website. If you wanted a donation to stay on the island, they suggested soap and toiletries, so we went up the road to the Leader Price and loaded up on some and dropped them off.