If they asked him to present, replying with "Sure I'd be happy to present, my fee is $xxx" doesn't seem likely to be construed as extortion and more than any ot

If they asked him to present, replying with "Sure I'd be happy to present, my fee is $xxx" doesn't seem likely to be construed as extortion and more than any other speaker charging for their time (be that research time, speaking time or both). If he had approached them cold it may have been a different matter, but that's not what happened here.