the problem I see with this bet is that even the chance is 1 in ~30k the user can win it in his first bet before the 29,999 losing bets. or what do I miss here?
Sure, there's nothing stopping that happening. You can be the poor sucker who invests before someone wins 99% of the bankroll, and then get diluted and never get your money back.
Bankrolling is a high-risk investment, treat it as such. Sometimes it seems low risk, because there's not much action happening, but it's just an illusion. (And that's even before you take into consideration the counter-party risks and what not).