I recently found these things and I dont know how much they cost. Someone can tell me? Also, how the thing of "slot 1" works? Someone can explain? Finally, this zombie virus is a unique emc item?
In order: 50r-ish It basically sells the item in slot one of the chest, the first spot (1st row, 1st column) Yes.
The [SLOT] signs work like a normal chest shop, except instead of selling the item on the sign that's in the chest, it sells the item(s) in that specific slot. For example, [SLOT 1] at the bottom of the sign could sell an enchanted pickaxe in slot 1, and people would be able to confirm the purchase to make sure that that's the right item. Also, if for example you type [SLOT 6], the items in 1, 2, 3, 4, 5, 6 would be for sale.
price depends on server, but you can expect to sell them from 25-100r, they don't sell too often as they really have no benefit, aside from the resistance boost, and is usually only bought for entertainment. Here's the link to the wiki... http://empireminecraft.com/wiki/items-zombie-virus/