Steam has the following on sale below (PC Digital Download):
Age of Empires II HD $3.99
Age of Empires II HD: The Forgotten $2.49
Age of Empires II HD: The African Kingdoms $2.49
Age of Empires II HD: Rise of the Rajas $3.29
Age of Empires II HD + The Forgotten + The African Kingdoms + The Rise of the Rajas (Bundle) $9.80