Telltale Games have reduced the price of The Penal Zone on the iPad to £1.79/$2.99 until February 10. The first episode of season three was first launched on Apple’s iPad platform on April 3 for £5.99/$9.99, so this is more than a 40% discount over the RRP.
However, the following four episodes were never to be seen on the iPad and there appears to be no imminent plans to rectify their absence, so you may be better off buying the package as a whole on PC, Mac or PSN.