bots can work.
but if you can buy it, or it doesn't work very good, or not for very long.
a bot needs steady adjustments.
And if you have a realy good bot, why sell it?
A well programed bot will not need a lot of adjustments since the economic theory is not going to change every week, the only adjustments needed will be if the API changes.
If basic economic theory is the only requirement for becoming a professional trader then there would not be any trading challenges as anyone could learn and become expertise with economic theories.
The basics of economic alone will never help anyone to make profits from trading, but we must need to react different market situations accordingly, otherwise a trader will be thrown out of market very soon. So I believe, coding a bot to cover 'all' market conditions is not practically possible.