First off, you are comparing apples to oranges. Gentoo-Portage.com is more than a decade old and once hosted a very active website. You are comparing that to a name you just registered. Obviously any domain, no matter how ridiculous that has a large active website is going to go for more money.
Second, do you see what that site is now? It's a parked page. Which could very well mean that it didn't actually sell for that amount...you do know that not all auction results are accurate, right? I could very easily list my domain for sale, then have a few friends bid up the price to make it appear valuable when I try to sell it later.
Please, do learn a little before you start posting, newbie.