I think there is an alternative to using Photoshop - especially if you use a Linux based OS.
I've often heard of people stating that GIMP is a valid alternative - I'd argue it isn't. GIMP is fine for performing a lot of everyday editing functions - but it's lacking in quite a few key areas (most notably CMYK support).
I think as an alternative, rather than having Photoshop - which could be conceptually viewed as an 'image IDE' - it's possible to choose to use a number of different command line utilities, plugins, scripts and applications to achieve the feature-set that Photoshop traditionally provides.
Creating and modifying imagery in this way, is arguably less intuitive, as workflows aren't so clearly defined - but there's the chance of matching (or possibly exceeding) what Photoshop makes possible.