You asked "You can't trade 5 pins for 1 pin if nobody has that 1 pin ;p". Well, someone has that pin because Disney didn't sell just 1 pin. I just have to find them. There are people trading nearly all of my wants, they just don't reply to me.
True, there are (typically) multiples of any one pin in existance, but not all of them are in circulation. A lot of them may be in people's collections and they may not even trade anymore. Some could even be overseas as a result of trading! Also remember, that for your harder pins, just because there are people with it marked as a trader doesn't mean they are actually trading it. Some just use Pinpics as an inventory tool and put everything in the trading bucket. I hate that....but they do.
Also, there are a couple of accounts on Pinpics that I'm really suspicious about and wonder if they are even "real". They showed up out of the blue and have all these amazing pins listed. Old collector returned? ....maybe.... Someone playing games and listing pins that they don't even have? .....also possible..... I'm not saying that is your problem, but even a pin with 5 people "trading" it could take a year or more to acquire, and that is if you are being persistent. The grails I just got took me several years to get and even though I had good traders (in my opinion anyways) I had to go out and find what the other person wanted to make it happen, which of course, was also a very difficult pin to get.
In a nut shell, you've got to be patient. It sucks...believe me, I know. And if you are trying to ferret out these old pins, you may be barking up the wrong tree. From the poll and the people that responded (which are most likely the more active members), half the people on DPF have been trading for 5 years or less. So, if you haven't been able to find your wants, chances are slim that they will be able to. I'm not saying that you shouldn't keep advertising and looking here, because you could get lucky. But you're going to have to try every avenue you can. People here can only do so much and they do try to help where they can, but when you are talking about super tough pins, there is only so much they can do... For tough pins, the best that can be expected of other forum members is to keep an eye out and alert you if they see something. Doing an all-out search for these pins isn't practical for most members because they have their own wants to worry about, so that falls to you. You aren't getting responses from here simply because nobody has any leads and there is nothing you can do about that.