A funny thing happened on Instagram during New York Fashion Week. Designers began posting behind-the-scenes photos of their fashion shows, and they were including lots and lots of details about the models' manicures. The idea, naturally, was cross-promotion with the brands they were using. Essie was big, as were Deborah Lippman, Sally Hansen and butter London.

This was all happening at the tail end of red-carpet season, during which the E! Network introduced its "mani-cam": Celebrities being interviewed on the red carpet were asked to stick their hand in a little box -- complete with a red carpet and a camera -- to talk about the details of their manicures. It makes sense, as nail polish is big business these days. ($768 million in 2012.) Most high-end lines create seasonal and/or limited collections (butter London, Essie) or include nail polish in their overall seasonal collections (Chanel, NARS).

I have a pretty extensive nail polish collection, so I dragged it out to see what I could find to re-create some of what I saw on Instagram. And what I found was this: I'm a sucker.

I keep my manicure supplies in two baskets: a smaller one that sits under the coffee table in the living room, and holds my "everyday" supplies like polish remover, cuticle cream, hand cream, and my most often-used polishes, base and top coats. In the bathroom is a larger basket that holds the rest of my collection of polishes. As I lined up the contents of both baskets, my husband peered over and said, "Jesus Christ. Those things are like your baseball cards or something."

It became apparent that I had a lot of duplicate colors -- "dupes" in beauty blog-speak -- in my collection. A little quick-and-dirty math revealed that my current collection is worth about $700. Seven. Hundred. Dollars. How did I spend seven hundred dollars on NAIL POLISH?

Some of the duplicates made sense -- most of us have favorite colors and buy things in various shades of those colors, right? So having a few neutrals, a few reds, a few grays in similar shades is no big deal. But what really surprised me were the similarities between seasonal collections. For example, the Essie 2011 Fall "Carry On" Collection and the Essie Fall "Stylenomics" 2012 Collection both contain tan/nude shades with purple undertones (Glamour Purse and Miss Fancy Pants), both of which happen to closely mimic "Merino Cool," a color in the regular collection that originally came out in the Fall 2010 collection.

How many tan/nude shades with purple undertones does a girl need? The answer is apparently "a minimum of three."

I noticed the same "dupe" situation when I compared my bottles of "Carry On" (Fall 2011), "Skirting the Issue" (Fall 2012) and the Essie regular collection "Bordeaux."

There is this theory that in bad economic times, women indulge in small luxuries -- cosmetics like lipstick and nail polish -- instead of bigger-ticket items. But are we really saving any money if these "special release" collections are releasing the same colors over and over, and we keep on buying them? Putting a new date on the same colors once a year and calling them "limited release" seems like a great way to take advantage of this phenomenon.

The answer might seem as simple as "buy from other brands," but like all things in fashion, collections from one designer or company tend to be in line with what the others are doing. Essie's hottest color of the moment is "Mint Candy Apple," which is not all that much different from butter London's Spring 2013 "Fiver," and everyone has a bright pastel pink right now -- Deborah Lippman's "Groove is in the Heart" (from the "Girls" collection), Essie's "Madison Ave-hue," OPI's "Vintage Minnie Mouse" collection. And we don't even have time to talk about the "new" nail sticker fad, or the celebrity and/or movie and/or television show crossover collections (OPI + The Wizard of Oz, OPI + Mariah Carey, Deborah Lippman + HBO's Girls, et al.)

It seems that these cosmetic companies, they are on to us. It might be time to seriously consider just using up the nail polishes we have and maybe, just maybe, actually going to Europe -- instead of buying nail polishes named after European cities.