There are actually times were the multiplier gets higher than this, everything is all programmed and I think they can increase up to this level to gain more attention and lure people into playing... no gambler in his Right senses would take such a huge risk..no matter how small the stake might be it would be absurd to watch it go beyond x500...This game is capable of changing your life in a day and also capable of wrecking it ..but I don't advice anyone to focus on this game, because in the long run you'd end up losing more than what you win.
Also, I believe that it only goes way upward when the remaining bettors are in small bets. I have never seen a crash game go x5 when there's a gambler who plays 1 BTC per bet.