another possibility is that as a trader evolves, his/her trading plan/strategy changes over time.
an old, discarded idea may be easily offered for sale, or freely disclosed, in the knowledge that the better, current idea is secret.
for example, an old idea may well generate 20 pips a day, but a newer, undisclosed system may generate 35 pips a day. you get the idea.
indeed, a trader may well post pics of a trading plan :whistling, but with altered settings. this allows to offer the general flavour of an idea, without revealing anything specific.
this means that ideas for sale, from a genuine trader, may well be profitable, but not as profitable as the current, secret rule-set. this does not apply to marketeers, who are not traders, merely salespeople.
I love the default cynicism T2W seems to engender :cheesy:, but there are degrees of shade rather than just black and white.