It's like a weave for your eyelids!
They don't come off at night and don't need to be reapplied like glue-on lashes. Convenient! Also stupidly expensive! The first set can run anywhere from $150 to $300. And that's just the bottom-shelf stuff. Some fancy-shmancy, ultra-rich, ultra-vain women get extensions made out of mink ...
It's like a rodent for your eyelids!
... which cost at LEAST $300 per set.
Not only are these extensions money pits, they're also incredibly time-consuming. Getting a full set takes about two hours. Getting them "filled" every few weeks (because they fall off) is about one hour. That's $1,500 per year spent solely on having the prettiest eyelashes possible, not to mention the time commitment of a cumulative total of an entire day spent sitting in a chair.
I'll admit that I'm vain 110 percent of the time and the way I look is important to me. However, the difference between eyelash extensions and simply wearing mascara or even glue-on lashes on special occasions is not that huge. I've never met a person that was like, "Oh, she'd be so much prettier if her eyelashes were longer!"
In fact, some surveys and studies suggest that men are actually turned off by fake eyelashes.