You'll find that unless you sell an impulse purchase (sub $35 price) targeting developers HackerNews traffic doesn't equal sales. Being that we sell accounting software for small business the traffic really doesn't affect our revenue. Overall programmers are highly critical of software applications, giving the most judgement support requests and demanding features deeming them "easy to build".

On the other hand, if the strategy is not directly applicable for your business, that does not suddenly become a 'busted myth'.

Though, I fully agree with you - as long as you are targetting narrow audience, getting 'general' traffic will not magically increase your sales.