robot is not made for making money. It does made to trade automatically.
A robot is made based on manual trading logic.
There are 2 type of sellers:
First type is (and most of the sellers) are selling dreams. They are either cheaters, or dreamers who think that they are making great job.
Second type of seller is not too much. These guys sell their robot for different reasons. Non of the profitable long term EA can make big money in short time. If the author does not have money in the pocket, he may choose to sell and collect money. Another reason is, most of the profitable EA on the market is outdated. What I mean is, it is still profitable but the author uses an updated version and sells the old version.
Do not buy any EA without a live account minimum 6 months history. Do not trust backtests. Backtests are good for optimization purposes. But will not quarantee the same behaviour in live accounts especially high frequency ones. There are some coders in this market, probably under 14 years old, has no money but intelligent. They sit and code in one week with friends and put it in the market, dreaming to get a lot of money. You can easiy catch such profiles. Keep away from them, whatever backtest they have.
Summary: DO NOT BUY ANY EA WITHOUT LIVE ACCOUNT WITH AT LEAST 6 MONTHS RECORD.