Unusual I have a few sets of the buffalos. Those would be an unusual comparison as they were made one year only. Some just had money when no one was buying. That left low numbers of coins struck in 08. The Prosperiety 08 sets also have done fine & the uncirculated " W " coins. On the average smaller coins just cost more per unit but do demand a bit more than the larger pieces per ounce.
Buy now Buy now usually has a premium over a standard auction up front. It is like a sale, -10% off of what base ?