You cant say if these things work based on 6 months they are...

You cant say if these things work based on 6 months they are quoting - in regards to mechanical systems if you can find one data set where the system doesn't work then the system does not work.

Secondly, when they quote their trades and returns you need to be careful. The trades they are advertising may be ones taken with the systems but they may not be the entire amount of signals given. eg. they quote 15 trades, but the system they are using actually identified 40 and they don't give you the results of those which may drastically alter the expectancy of the system. for example there futures system which is only $349 a month gives trades ranging from soy bean futures to t-bills covering a wide array of correlated markets yet only identified 15 trades. I would ask for some audited brokerage statements before i even considered it.