I cant say it costs more than normal playing since there are always 2 possibilities.
In normal play, there is no guarantees that you'll get the free spin after losing/wagering equal amount to the feature's price.
While on other side, there is no guarantees that a buy feature will give you a good outcome or at least give what you have paid back.
Personal opinion but imo its much better to buy those bonus round directly instead of trying to get one naturally if you are playing on a high / extreme volatility slot . Its much easier to get one on medium / low volatility but sometimes it might takes over 200 spins to even get one on those high volatility slots
This is personal preference but if you love to watch those spins animation as well as the suspense while playing then its fine though
The BNB dice wager race is coming to an end in a couple of hours. Number 50 has till date only wagered 50$ (in BNB coins), so this can be achievable for some people.
1 BNB stands at $45 and all you have to do is to wager 1.2 BNB at 98% chance to win to get into the top 50 places paid, thats not a bad deal if you ask me.
I just checked the leaderboard, but I don't recognize anyone from BCT. Guess BNB is not yet the preferred coin to gamble for BCT members

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Some people probably dont use the same nickname they used in bitcointalk but most people are used to gamble with eth, trx and usdt nowadays so probably yeah