People try and price stuff crazy at garage sales sometimes. If they are willing to go through the hassle of selling it on eBay, let them get the money, otherwise let the stuff sit.
As far as finding stuff and making offers, it goes both ways. I went to an old lady's house one afternoon who called me about my classified ad about star wars toys. She pulls out really nice original carded 12 backs in beautiful shape. She set the price crazy low ($50 for 5 or 6 figures at the time, I can't remember), I countered at $150, and got them. I think I turned them in about a week for around $800.
I've also popped on the asking price (even if it was low) and laughed my way to the bank. But there are times you buy a collection, and have to scrape every nickel out of it to break even.