Several years ago I decided to build a 19th C US collection. I decided to only collect used stamps and avoid all the gum questions ie. OG, NG, regum, LH, and MNH. My goal was to build a collection in which EVERY stamp was eye catching, This evolved to having a theme for each issue. All my banknotes had NYFM cancels, I looked for star cancels on the Colombians, some issues were all geometric cancels and others were clear CDS etc. As to condition I could overlook a nibbled perf or a corner crease if I liked the stamp and I would always accept a straight edge stamp.
For about 3 years I prowled
ebay looking for candidates and was able to built a collection that I really enjoyed. The point of this story is that for building a collection like this
ebay was a great resource, I wasn't buying 100J stamps or MNH $ Colombians or expensive coils, but for the mid level? stamps I wanted
ebay was a goldmine. I had no problem with any of my purchases, everything was received in good order and just what I expected. Now for the best part.
When I got to the point I didn't want to continue the collection because the stamps I needed were too expensive I decided to sell it. Over the next couple months I sold the stamps on
ebay and in the end sold the collection for almost exactly what I paid to build it. You can't beat that!
I think every stamp collector should learn to sell on
ebay, it's a valuable skill. When you buy a stamp you learn what it costs, when you sell a stamp you learn what it's worth.
As for the original question, on my statistics page
ebay reports that sales in the Worldwide Collections category are down 10% year to year but my sales are up 70% in the same period. The principal reason my sales are up so much is that I was able to buy 4 very strong Big Blue collections in the last 6 months. Much to my surprise I recently bought an excellent collection from Noblespirit. My sales are excellent with strong bidding and I average 40% new customers each month.