Many people collect perfumes and colognes. So it is not surprising that they are big sellers online. For example check out a recent sale on Ebay.
Vintage Christian Dior Cologne Miss Dior 4 FL.Oz. Original Box Unopened
A quick look at Etsy showed this
Vintage Rare Womens Lauren Ralph Lauren COLOGNE Eau de Toilette 4 oz
Now, here is an interesting article on the popularity of perfume bottles for resell value..
Here is a video by a perfume and cologne collector