There is so much variability in that data, depending on work setting, years of experience, etc. (And apparently I make WAY more than average for my field of work and years of experience...wow, it sure doesn't feel like it.) So you can't really say "how much people make when everything is added up." It varies tremendously.
I have seen positions go for $55k and require 3-5+ post licensure, and I've seen positions for people coming out of post-doc for $75k+ (with a package bumping it up to $100k). I personally would be very unhappy if I don't gross at least $75k my first year after fellowship, though I understand my expectations and willingness to put in the hours to make that happen are different than other people.
I think as long as a person is properly trained, has some sense of business skill (or can find someone to help them), and is willing to put in some work up from....they should be able to make $100k+/yr without too much trouble. <--in regard to private practice + a side gig. Most people run into issues because of time/commit/lack of desire to do more than take a position somewhere. There is also a HUUUUUGE issue of mariginalization, but I'll leave that for later when I have more time.
Where people run into the most issue with compensation is they trade comfort for $. A staff psychologist position easily pays 40%-50% of what you could make on your own, but there are perks that come with it that are different than private practice folks. There are people who take staff positions and then add on. There are other people who branch out into less common areas and do quite well. I plan to be in the latter group (eventually), but it seems that most psychologists are rather risk averse.
I've already been a paper milliionaire (until the tech. market crashed), and I learned risk is what makes people money, since far fewer people are willing to go there. I'm assuming I'll bust a couple more times on ventures, but all I need is one venture to go well and I am set. Very very few people are willing to go that route, but that is why the "average" (not sure mean/median/etc) that psychologists make is probably $75k. There are definitely market forces at play too, but we are one of the most risk averse professions out there.
The VA payscale isn't so bad, and it is quite comfortable once you factor in the cost of your healthcare (which is very good), the liberal time off, etc. Obviously not everyone wants to work in that environment, but there are options.
I really could write a lot on this, but I have to get some paperwork done, so I'll defer for a later time. This is one of my biggest pet peeves about our profession, and one area I think I can capitalize in the general risk averse nature of my bretheren. Psychology has so much to offer, and yet too many people who offer too little of what is actually needed.
At the end of the day 90% of psychologists will take traditional jobs, making decent money, and may or may not be completely happy. I think we have happier people in general than other places, but the last position I'd want to be in is chasing after every last session check because my electric bill is due. <---THAT is what I am most averse to at the end of the day.
Personally, I like the idea of taking a staff position and "adding on" some private practice, teaching or consulting work. I could see eventually making private practice my sole source of income, but as someone who is not naturally entrepreneurial and who left a pressure-filled first career for something more fulfilling, I'm okay making a little less (at least in the beginning-- I could see this changing later on). I definitely do not like the "chasing down the fee" aspect of private practice, but the depgree of autonomy that comes with being your own boss is appealing.