You can't sell wither heads for more than 5k, nobody gets them because you get one about every few hours if you're lucky and even after that you aren't able to sell them for much.
It's not even considered grinding, due to the difficulty being set to low. It's basically impossible to get them.
Gabriel, no those are meant to be created by players and sold to players.
There are about 1-3 per nether fortress, 4 if you're lucky. At this rate it takes hours to find one. Say you find 10 nether fortresses in 5 hours while using looting 3, and each fortress has 3 skeletons. 10 * 3 = 30 skeletons to kill. The probability of getting one head is [1 - (1 - 0.055) ^ 30] = 81.68%. The probability of getting 2 heads can be solved by using a binomial expression, P(X = 2) = (30! / (30-2)! * 2!) * 0.055 ^ 2 * 0.945 ^ (30-2) = 27.00%. The probability of getting 3 heads is 14.66% (use the calculator at http://stattrek.com/online-calculator/binomial.aspx). It's too time consuming to get wither skulls by yourself which is often unsuccessful.
It's grinding cause it's difficult and you have to run around a lot and wait.
Even worse than MrNuggly's idea.
Yea, I see how that would kill PvP on the server, especially in the wild, people would just have SB stuff and dominate, while new people just have a standard enchcanted sword or axe... sounds like me... D: I'm a n00b at pvp cause I'm a police and can't invest in that stuff
Yeah they are difficult to get, but that way noobs do not get mythic and build withers easily.
