GamersGate offers Steam downloads of Middle-Earth: Shadow of Mordor Game of the Year Edition for Windows for $4.88. That's the lowest price we could find by $11, excluding the below mention, although we saw it for a buck less last month. This edition includes all DLC.
A close price: CDKeys offers downloads for $5.19. New customers can provide an email address on the CDKeys Facebook page to get a unique coupon code that cuts an extra 5% off.