There are 4 types of mounts that are free after rebate. They range from $69-$89. All of them are free after the rebate.
According to the rebate form there is a limit of 1 rebate per product per address, so you would get a rebate for one of each of these if you decide to buy all four.
Shipping is free if you order $99 worth of items from PC Connection, so if you order 2 wall mounts your shipping will be free as well, otherwise expect to pay about $12 shipping if you order just one.
Rebate Linky (Purchase between 10/01-12/31, postmark within 30 days of purchase)