Hi
Well, personally I'm in the process of developing a trading bot ! So what I say comes from experience.
If you are running a bot on time-based candlesticks, there is a small chance of winning on lower time frames, most of the scalping bots being promoted will never work. Very few of them can be profitable on higher time frames and the result.... is tons wors than doing trades manually.
So, why someone would buy a bot that trades 12% per year?
1- europian and American banks won't give profit above 5-6 % per year, so, for many people, 12 percent is a lot!
2- when a bot is profitable in one pair, if you can fine-tune parameters for more pairs, this means the total gain will be multiplied by the number of pairs
But...
if you want to know the real secret...
When you have a bot that is giving you nothing but lost on time frame candlesticks.... try it on non-timeframe based charts like Renko ! The bot I am developing, on 1-minute candles, would go down with a 30-degree slope until it would make the balance zero. But on Renko charts, it gives more than 50$ gain in month with 0.01 positions !!! I will let you do your homework about the reason this happens on a chart like Renko.