Bonus buy math weird

Has anyone else noticed how sometimes the bonus buy price doesn’t line up with what you’d expect for the game’s potential? Like, I swear I’ve seen slots charge way more for a bonus than what the average bonus round actually pays. Did some math on one last night and the advertised RTP is 96%, but after three bonus buys, I was down almost 60% already. That’s not just bad luck, right? Maybe I’m getting paranoid, but it feels like the price for bonus buys is set more for player FOMO than for actual payout rates.

Do you guys just ignore bonus buy cost vs potential or do you actually run the numbers before buying? Anyone have a method that keeps them from going overboard chasing those "worth it" bonuses?