...I used an arbitrage bot a few years ago and it worked well, but unfortunately the trial for a few days was just a trial and then there was a fee that I needed to pay to enjoy the premium features.
Well, if the cost of the arbitrage bot is lower than the profit that you earned, then you can safely make such a purchase. After all, you write that you were satisfied with the arbitration bot, so why didn't you buy a premium subscription then? Or is the subscription price higher than the profit received?