Newegg offers downloads of a selection of security and anti-virus software for Windows, Mac, Android, and iOS for $19.99. (See this price on each software's product page.) Some notables, all available for at least PC, Mac, and Android:

• AVG Ultimate 2015 Unlimited Devices 2-Year for $19.99 (pictured, same at Amazon, low by $30)
• Webroot SecureAnywhere Internet Security Complete 2015 5-Device for $19.99 (same at Amazon, low by $20)
• Kaspersky Internet Security Multi-Device 2015 5-User for $19.99 (same at Amazon, low by $25)