you should be happy that there are still people willing to pay good prices for posters. Most of the hobby is made of buyers and bidders looking for the cheapest price possible and it's difficult to make a profitable business selling $10 posters or especially $1 posters for 99.9999% of people.
don't forget that someday you may all want to sell your collections also, and as Mel pointed out, he was in for $137k and when he got out, he got back $95k and when you consider his collection was not largely inexpensive posters, that is by itself, a message to what you can expect when you sell out.
Sean and I have had this discussion many times and with the exceptions of material we bought many many moons ago, neither of us expects to break even on our own collections. So when there is a buyer or two or three willing to pay good prices, it isn't just better for the seller of that item - it's good for the entirety of the hobby