Due working in a record-store, I come across related thing all the time. Meaning, that in Finland, so many people keep reading the stupid articles about "vinyl is in again" and "you might have valuable items in your shelves" -category, that it has totally clouded the reality.
Just about everybody thinks they are holding some utterly expensive and rare items, while almost without exception, they are not.
Related to this, I had quite amusing discussion with one customer who brought pile of CD's and I told how much I'd be willing to pay for them, and he said "then I'd be losing money". As if it would have ever been true that selling your unwanted, used, bulk CD's is about "creating profit".
Most of the time, one would have to accept that used records are like used goods in general. If it isn't something utterly rare and exceptional, it's something in similar with items of flee-market discount bin - not antique trophies hidden in locked vitrine.
It's hard to be sure what are the prices that actually are paid. Just recently, friend told that there was guy selling 80's industrial tapes with 15-25 pricetags at discogs and he made offer c. 5 euro each for bunch of them. And deal was made instantly. Others may see expensive items disappearing that they have drooled for months, but perhaps didn't realize they didn't necessary sell for the mentioned price but fraction of it? One can always say that "market defines the prices", but can one make this assumption based on 1 case of item being sold? Often you see specific items sitting year after year for sale, which indicates price is too high. If it gets sold at some point, is it sign of right price, or isolated case of one desperate collector in moment on brief "well, fuck, it hurts only one" -feeling. Which will never happen again, but few opportunists keep their personal collection listed online just to hope this happens someday again.
When case is tapes, limited to XX copies, it's too bad that good noise tapes are at hands of dealers, not the listeners. Money you can make from some noise tape is so small, that it seems utterly stupid to vault items for years in dream of making 5usd or 10usd "profit", when you could just sell it for price that gets it into circulation.
However, I think current times appear that second-hand profiteering isn't that huge issue, since we live now moment when it can be CHEAPEST and easiest to grab noise. If you are willing to give it a try for other things than rare Proiekt Hat or Prurient, you can get shitloads of great stuff for bargain prices.