You're crazy. Good luck, though.
He's not crazy, he's really smart.
His first bet was 200 ETH. If people get in line, he doubles his investment. If they don't, he sends another 200 ETH and gets 400 ETH back.
As it is now, if nobody else puts in, all he has do is add 100 and he will get his 400 and some idiot is out 100eth.