Whilst some may think that justify is a rather strong term to use here, I think that it is perfectly appropriate as there are far too many people making cents online, but working themselves to death for it. If you ask me, we all need to take a serious look at what we are willing to do online for a couple of dollars, and how it translates to what we'd do offline. Remember, a 9 hour job offline pays on average $50,000, whilst online you are pleased when you receive $100 a month.
I think for many who work online, there are either barriers to that 50K/year position or significant costs that are avoided by working online. Most of the people I know who are trying to build an online business have children who would require costly daycare if they worked out of the home, or have retired and aren't interested in giving that much of their time to an employer, or live in rural areas with few job opportunities, or are disabled and can't handle the demands of most full time jobs, or some combination of all of the above. And most don't have the education required to earn 50K - around here, that takes a either 4 year degree and a little professional experience or a great deal of experience in a skilled trade. There's no real point in comparing online earnings to average full time salaries if that average salary isn't something you could command in the workforce; the better starting point is to compare what you would realistically earn after expenses from a traditional job vs from working online, and then factor in the intangible pres and cons from there.