That's OK, Marijn. It seems to me you're asking in good faith. I'd contact the sellers mentioned above to get an appraisal, then take it from there: either sell the pipes to them or try eBay. If I acquired something I am unfamiliar with, I'd also ask around to try to find out the real price. Personally, I don't see what's wrong with that.
I have emailed Steve from pipestuds. Thank you for your reply!!
Cheers, Marijn from Belgium