Is a casino bonus actually worth taking? Calculate the true expected value before you claim.
Expected value (EV) tells you the average outcome of an action over many repetitions. A positive EV bonus means you'll come out ahead on average — but this requires playing with exactly the right RTP and game contribution.
A 35x wagering requirement on a 96% RTP game means you lose 4% of every bet placed. On €3,500 of wagering, that's €140 in expected losses — more than the €100 bonus received. The bonus is negative EV.
Even negative EV bonuses can be worth taking if you enjoy playing and were going to deposit anyway. The bonus reduces your net cost. However, never deposit purely to chase a bonus.