Steam is having a summer sale until July 5th. http://store.steampowered.com/

I bought a $20 Steam card at Atl. Superstore in anticipation for the sale. (Rather than using a credit card or PayPal.)

Purchased: Portal and Portal 2 as a bundle for 2.46 http://store.steampowered.com/bundle/234/Portal_Bundle/
Rochard + 1 DLC for 1.63 http://store.steampowered.com/app/107800/Rochard/

The games are similar, in that a certain sequence of events have to occur for you to move forward.

Dishonored 3.74
Thief 6.59
Deus Ex: Human Revolution 4.39 (This is one of my favourite games.)