They say that everything has a price—and this axiom apparently includes Xbox One achievements, judging from recent eBay listings.
Thing is, these achievements are extra special—they come bundled with the limited number of 'Day One' editions of the Xbox One. As the name suggests, these are consoles made to commemorate the launch of the Xbox One. Only those that pre-ordered this version of Xbox Ones will get the special 'Day One' achievement.
Unless, of course, you buy it. The achievement comes in the form of a code, which anyone can redeem—naturally, they've shown up on eBay. As of this writing, most codes seem to be going for about $30-50 dollars. That's about as much as people are pricing weed emoticons on Steam.