You've been there… scratching down the new billion dollar idea on a cocktail napkin, then going home and finding out the domain is already taken. The other half continues to collect domain names waiting to make the billion dollars. Most of us are somewhere in between… domain owners who aren't using their domains will typically sell them. And the entrepreneurs that wish to buy them are willing to spend a few bucks to get them.
Registered domains that don't have a website associated with them have often been purchased by speculators who are banking on making a profit from buying a name they hope will be irresistible to a future purchaser.
Don't quit just because your domain is taken! I've sold a domain for as much as $10,000 (quite a few years ago) and bought them for as low as $100. It's a fun game of cat and mouse between the buyer and seller… but if you need that domain, you can get it! Check out this infographic from Whoishostingthis.com on how to buy a domain that's already registered.