It's a bonus more similar to bonuses on various other casinos where there's a wagering requirement (it's not just free money). If you want to play Hi-Lo, it might be worth taking if you were going to wager near the rollover amount anyway, but it is a -EV bonus (25x rollover with a 5% house edge) and you're expected to lose 25% of your stake.
Completely right.
Here I give an example to make it more clear.
I claim 1000 Satoshis. 1000 Satoshis will be deducted from my balance and I will have 2000 Satoshis on my bonus account.
If I play HI/LO game and I wager 1 Satoshi 1000 times, the house edge guarantee that I will lose 50 Satoshis. (In long term, it is 100% true and that's why I considered the amount of each bet only 1 Sathoshi).
To become eligible to withdraw my balance from my bonus account, I have to wager 1000*25= 25,000 Satoshi. So, I will lose 1250 Satoshis. So, I become eligible to send the entire balance from my bonus account to main account when I have only 750 Satoshis.
Thanks to both hosseinimr93 and DarStar_ for the responses.
In fact, I think its an even worse proposition then your example highlights as you have to bet through 25x then entire amount, not just your own contribution. If Im correct, it would mean you would expect (if allowed) to go into debt of 500 satoshis on average for every "succesful bet through attempt."
Ah well, nevermind, my instinct was in line with this but I wasnt confident about my calculations. Thanks again.