The French government's spokesman said in an interview published late today that foreign tourists will have to start paying for Covid tests as of next Wednesday, July 7.
He said the charge for PCR tests will be 49€, and for antigen tests, €29 (the latter is fine and meets the the requirement to return to the U.S.).
Here's a link to a newsflash quoting from his interview, which first appeared in Les Echos.