Is this also true with regards to charging more as a consultant/freelancer or about negotiating a better salary? We see a lot of stories like that on here too.

The problem is defining 'greed' is hard. Is a software developer asking for a $100k salary inherently 'greedy' for earning more than double the average US wage? Is someone earning $20k and pushing for a raise to $30k 'greedy' because someone in Africa lives on $1 a day?

Earning $100-150k in a year from a few e-books might seem 'greedy' in some ways, but then you could compare it to the textbook author who supposedly spent $24m building a house from the profits on some calculus textbooks.. ;-) http://castingoutnines.wordpress.com/2009/04/06/where-the-mo...

Rather than have such (unresolvable) debates, it tends to be simpler to rely on economics and charge what the market will bear because while it's not perfect, it's as fair and objective a value as could be arrived at through even the most perfect of debates.