Thank you China Girl.
What happens it many perfumes houses are bought out by others.
LVMH bought Guerlain and Dior amongst others, Proctor and Gamble etc bought up others.
Then what they do is see how they can make more money for themselves, so that mean using cheaper ingredients or reformulating. As a teenager I loved Femme by Rochas a gorgeous leather chypre. Rochas was bought out a few times by different companies, then in 1989 they totally reformulation Femme and added cumin(why is a mystery?). So the Femme you see today smells nothing like the one I remember, I was lucky and managed to get a vintage pdt version on ebay which smells how I remember. On the perfume boards it is an on going moan about perfumes being reformulated. So that is why vintage is they way we try to go. The Americans are lucky they have what they call yard or estate sales(someone's granny,auntie etc dies and the family clear out and sale everything. Bit like our car boot sales only held in their yards), they are a gold mine for older versions of perfume really cheaply.
Ebay is the way to go, but you have to be very careful incase of fakes. Chanel,Dior,Creed are the most faked. It might take awhile but search look at the photos and ask the seller questions. There is the dread of the perfume having gone off too, so again look at the photo and ask questions. Oh and some seller take the Michael in asking price too.
I mentioned my bottle of Caron's Fleurs de Rocaille 1960, 75mls parfum(or pure perfume as its called), the guy selling had it in the wrong section for a start. It was still sealed with the gold wire so unopened. Now this should have went for hundreds(I watch auctions and there are some perfumes which go for really big big money. For those who are real collectors). I had it on watch and no one bid, I was shocked so finally with 5 minutes to go I bid and won it for £23. Now the top notes are a little faded but it is still Fleurs de Rocaille(its famous for being named in Scent Of A Woman by Al Pacino) created in 1933.
On the beauty boards people sell or swap stuff as well another way to obtain.