Here is a thread that will check for you if a robot that you plan to buying from MQL5.Com is worth it or not

most robots are a scam and if you have a doubt i'm sure the community can bring their honest opinion over if it's a scam or not

3 types sof scam :
1) the robot stores trading times within the executable (usually they have big files for no reason)
2) the robot is a tick scalper (very little trades in duration) : while sometimes they may work on some brokers, most of these types of robot will fail live
3) The robot is curve fitted to data, meaning it will perform really well in the backtest but will fail with new data. This is a bit like 1) but more fancy

Jeff