nop v1.5 features

in admin when you edit product varient, below     price     there is
     Product cost:      

is this used anywhere in the store or is it just for admin information

Cost price is the actual cost of the price,  Just price means List price which is to be displayed on the website to sell any item but Cost Price is the actual cost which admin is paying for that item, So it's just a way to keep a track of admin's inventory/ profit record

Yes this is just for admin Information to see how much profit he/she is making, it's just like you got a pencil for 10 bucks and selling it on the website for $12, so $10 is your Cost Price, and $12 is your Price(List Price).

Hope it Helps