Arbitrage is a race: a good arbitrage bot will take advantage of differences in price, before anyone else is able to. By performing the arbitrage trading, the difference in price will disappear, so only the fastest traders will be able to profit.

So with this in mind, I am extremely skeptical of any arbitrage bot that is being publicly sold, as the user that purchases the bot will be directly competing with all other users that purchased that bot, and probably other people that have their own methods as well.

And so I think it is likely that the only person who is sure to profit, is the person who sold the bot!

Bots really work according to the given algorithm, but this is their advantage. For example, they can collect information about exchange rates on different exchanges and offer you an exchange. But almost all of these programs are paid and subscription is available for several months at a time. Some, for example a BibitBot, have free versions for several days.