I don't know if it can be compared to Lightroom, but I'm totally blown away by Photogene 4. It works out to something like $3 and allows adjusting levels, exposure, colours and the usual cropping and filters.
You can also see and edit EXIF information, as well as add locations.
If I'm not mistaken, it edits RAW as well, but I'm not sure.
Still, amazing value for money. Lightroom at $10 per month - not so much.