Ah, well, since I have your attention, I'll give you the other side of the coin. The key to getting good stuff from people is how you make them feel about giving it to you.
Most people think thrift stores sell the stuff people drop off there. That's far from true. They get their product from a lot of places -- retail seconds, charities, sometimes even new.
Direct donations are the worst. It's still positive expected value after you collect, sort, and label it all, but sometimes only just barely. Ever notice thrift shop donation centers sometimes have terrible hours? They don't want the stuff that bad!
In direct donation, people give you things they think you're going to sell. They think they're doing you a favor, they think everything has to have some value and anyway, you guys are the experts and at worst you'll just throw it away, right? You get lots of garbage.
One of the things I think people don't understand is the "where it came from" factor. My tennis shoes have some value to me, even though they're pretty beat up. I know where they've been. They've always been mine. I'd cheerfully spend $40 to get them back if they'd disappeared tomorrow.
But to a stranger they're stinky, dirty, beat up, and they don't know where they've been. Zero value. Negative value, even.
Anyway, when people are assessing their own stuff for resale value, they do a pretty terrible job, and it's my private theory that the above is responsible.
Anyway.
The boxes we got with the highest value were from charities. Those signs that say, "Donate your quality used goods to the center for (cancer|mental retardation|war veterans)" . . . those goods eventually end up being sold to thrift stores, and the typical quality is amazing compared to what people drop off. Five times better. Ten times better. More. Depends on the source.
Psychology is weird, and in the thrift business, it can be the difference between a (very) positive and (very) negative profit margin. Just what people choose to give you. I certainly can't begin to explain it, and would never have expected that the difference in the quality of donations to different causes would be so wide.
Just be careful, is all. In my (limited, unscientific, yet still statistically significant) experience as a junk sorter, stuff coming from the "we'll take your junk and resell it" message performs the worst. The very worst. "For the children" seemed to be about the best.
I have absolutely no idea how "purify your life" will do. Could be awesome. Could be terrible. I'm not optimistic, but who knows. People are weird.
If it does poorly, though, seriously considering donating the $10 to a (specific!) charity. That should help a lot.