Not a collector but I've accumulated 4000-6000 worldwide stamps years 1960=2010, from virtually every country, islands, etc, that I would like to sell. I'm in the early learning curve, but from looking on eBay
and other sites I see many, many stamps offered for sale at extremely low prices and very few buyers. My conclusion so far is that it likely not worth the time and effort to sort for very little return. Many are off cover, many on torn covers with postmarks. All stamps are from mail sent directly to me over the years. Dealers seem to have no interest. Thanks.