Prima already sells eGuides of what seems to be their entire back catalogue. Prices start at $6, which really isn't reasonable for GOG's pricing. Additionally, their guides are presented as DRMed PDFs, which is incompatible with GOG's goals; in order to read one you must first run its installer (seriously) and it can only be read with the included reader; attempting to open it in Adobe Reader or similar doesn't work. I don't think Prima would particularly like GOG's way of doing things.

Well it seems that $1-3 is about all the work that goes into many a prima guide. I've seen one or two that were okay, some that would be good if they got the information right and one or two that might as well be "Play game, you'll finish it eventually"
They'd never be something I'd buy. GameFAQs are just as crap but have the virtue of being free

I see game guides more as "artwork of the game and unique background tips"
and sometimes, they're kind of a review as well.
sometimes it's nice to just have the straight answer but I really don't see them as just guides.