That is only if you count every backer purchases something at every sale, what is a more likely is the majority of backers purchase something throughout the sale season here and there.
You offered up the image as something that was supposed to show what the majority of backers do. What it shows is that they don't spend very much, even if we assume they're as few as they let slip during the summer — the more there are of them, the less they spend. Now, this may not have been your intent with picking that image to illustrate your point, but
it is what it illustrates.
…which rather raises the question of what your point was to begin with? What were you trying to show as to the actions of the majority? I know they've published some kind of customer spending break-down earlier, which would probably serve you better.
I actually do believe that the website doesn't represent exact numbers of backers. i would cut that 1.6 million in half at least being that that numbers seems to go buy ship sells and not new opened accounts. I think, Im not sure tho.
Yes, it counts everything and everyone that has ever done anything on the site — the number of actual backers was said to be in the 500k region a couple of months ago, and in spite of everything, they've probably picked up a couple more since. But that's how you get to something in the half-dollar region (which, admittedly is a pretty wide margin of error): assuming just over 50% has given ¢50 each, and that $194k peak would represent a total population of 776k individuals. Sure, they spent as much again the next day, but that's still just $1 over two days — not the most grandiose of gestures from that supposed majority, now is it?