Worthwhile is not an easy question to answer in terms of Lab of Lunacy’s bonus buy options. Especially since there are so many offered in this instance, each with its own pluses and minuses.
Overall, they can be a nice addition to your general play every now and then, since the bonus rounds are always the best part of the game.
The lowest level Double Boost, however, doesn’t give you any guarantee, so if that’s what you’re after then it might not be right for you. Things like the Bonus, Super Bonus, and Lunacy Bonus, though, while they do ensure free spins, come at quite a cost. And experience shows that even with this, the ultimate payout is often lower than the additional stake invested by the player.
As such, determining if bonus buys are worthwhile is going to be a balancing act – between your budget, goals, and overall expectations.