How is this following the 1% house edge rule? I don't get the maths behind it.
House edge of 1% means that on average you will lose 1% of what you wager. So your expected loss by betting 1 BTC on this bet, is -0.01 BTC (same as any other multiplier). The only real difference here is you're effectively paying 0.01 BTC (amortized) for a (large) shot at winning 1.0102x BTC (or what ever). That's why cowbay (he was the first?) to call it the suckers bet. It seems good, but it's a *fantastic* deal for the casino and a terrible deal for players.
If you're interested in maths, check out the FAQ of bustabit it documents it a fair bit and we don't use a traditional "house edge" precisely to make it more fair for players who are doing these types of bets. (For instance, if you bet on bustabit @ 1.01x, you'll be paying a mere 0.009900990099% house edge, precisely because the house has so little risk) .