I forgot that there is an Autumn-Sale that will go until 28th.
Prices for both games did change:
ReThink: 4.99 $ (from 9.99 $)
ReThink | Evolved: 7.99 $ (from 9.99 $)
ReThink-Bundle: 11.68 $ (from 17.99 $)
http://store.steampowered.com/app/603800/ReThink/
http://store.steampowered.com/app/703500/ReThink__Evolved/
http://store.steampowered.com/bundle/4387/ReThink_Bundle/