Well, I suppose there is a 'value' in a way. If I am interested in a Buddy item I decide the number of points I am willing to bid up to for it. So, to me, the value per point is the market value of the item divided by the number of points I will bid. Probably works out somewhere between 50p and 1 pound depending on how much I want the item.
Each person will determine that themselves and, as in normal bidding, different people will place a different worth on an item. How easily individuals accumulate points may also influence the worth they place on each one earned.