Awww, forget them. Yes it would be nice if your neighbors treated you better, but sometimes that's the breaks. I'm betting this has nothing to do with you, it's just the way they are. So don't worry or get to upset over this, it's not worth it. And DO NOT feel guilty for refusing to buy your neighbor's junk! They're just trying to take advantage of you! Believe it or not, I had family members who used to do the same to me. I was a single parent for 10 years, and my son and I didn't have much money. They were always thinking I should be thrilled to buy their worn out garbage. Just say NO and don't think twice about it. And quit doing favors for them, unless you really feel like it. Nothing straightens people out like cutting them off at the knees!
I agree with the previous post. You seem like a nice person. You are right to say that you need confidence in yourself and you should not let them make you feel insecure.