Scented oils and resins, and the vessels which hold them, have existed since the dawn of history.
The Mesopotamians and Egyptians, like the Greeks and Romans who followed, burned incense during religious and civic ceremonies, and anointed their bodies with perfumed oils, ointments, and cosmetics. And of course, it was necessary to create special containers for those products.
Egyptian tombs have yielded containers made of pottery and alabaster, while archaeological excavations throughout the Mediterranean region have unearthed ceramic and glass containers made by the Phoenicians, Greeks and Romans.
Venetian and Murano glass makers made what are considered some of the most exquisite perfume bottles in the 16th and 17th centuries A.D., while the British mastered enamel and porcelain in the 18th.
By the 19th Century, mass production presented a growing challenge to individual perfumers and craftsmen, and the 20th century witnessed the rise of the great commercial houses such as Chanel, Lanvin, Dior, and Lauder. The individually-made perfume bottle was replaced with a beautifully-designed, but uniformly-manufactured product. The most famous example of this is the collaboration between Nina Ricci and Lalique Glass (http://www.infomat.com/whoswho/ninaricci.html) that resulted in the 1948 fragrance "L'Air du Temps" and the bottle with the dove (or doves, depending on the version).
Today, there's been a resurgence in hand-made and hand-blown perfume bottles. Created as works of art, these one-of-a-kind pieces are highly sought after by collectors, some of whom concentrate on a particular artist, while others purchase whatever appeals to them.
So, what are the factors worth considering when collecting perfume bottles?
The first is category: there are so many different bottles in existence that it is almost impossible to afford more than a tiny fraction, so it is necessary to specialize. Perhaps you're interested in atomizers, or figurals, or Josiah Wedgwood jasperware? A particular country (like Czechoslovakia), period (Art Deco? Art Nouveau?) or size? ("Minis" - miniature copies originally distributed as samples - are very popular.) And then there are color, company, favorite fragrance, etc.
The second is condition: does the bottle come with its original packaging? If there were hang tags or tokens, are they still present? Any or all of these can increase value enormously, so always buy the best, most complete specimen you can afford.
Third is rarity. Generally, very old (pre-19th century), hand-made, and signed pieces are indicators of rarity.
Fourth is aesthetic value, which is somewhat subjective, but over time, a consensus usually arises as to what is beautiful and what is not.
So, what kinds of prices are being realized at online auctions today? Well, a 1997 Lalique factice (a display dummy) just sold for $799; a 1930's Mickey Mouse went for over $800; and a Gorham Martelle, signed Tiffany, recently fetched over $17,000! Of course, these are exceptional specimens, but it pays to do your homework, so check out the following resources - you never know when you'll come across a "find" at a yard or estate sale!
Books
"A Collector's Handbook of Miniature Perfume Bottles: Minis, Mates and More," by Jeri Lyn Ringblum
http://digbig.com/4mbka
"Lalique Perfume Bottles," by Glen Utt
http://digbig.com/4mbkb
"Miller's Collector's Guide: Perfume Bottles," by Madeleine Marsh, Linda Bee, Lynda Brine
http://digbig.com/4mbkc
"The Wonderful World of Collecting Perfume Bottles: Identification & value guide," by Jane Flanagan
http://digbig.com/4mbkd
Websites
The Barcelona Perfume Museum (Museu del Perfum)
http://www.museudelperfum.com
287 bottles from all historical periods on display. History, links, more.
International Perfume Bottle Association
http://www.perfumebottles.org/home.cfm
Considered the largest perfume-bottle association in the world. Publishes Perfume Bottle Quarterly magazine and hosts annual IPBA convention. Check out their photo gallery, FAQ's, and links.
SolidPerfume.com
http://www.solidperfume.com/default.html
Devoted to Estee Lauder "solids" found in lockets, trinkets, etc.