A wag is a person who makes amusing or sarcastic comments on things often. It is definition 3. here: http://www.learnersdictionary.com/definition/wag In this case the 'wag' is joking that Amazon is charging people money for something they can already get for free.

I immediately understand "wag" to mean a person who makes witty quips on topical issues. Nothing much of substance, but in this situation the writer suggests that there is something more to their sarcastic observation.

That word has so many different slang meanings, that I'm not really sure which one applies here. However, I read it as a mild insult to people who "wag their fingers" at the Kindle, as in people who think Libraries are better and books should be printed on paper, etc. In that sense, it relates to the actual movement of wagging a finger at something you don't like (typically "wagging a finger" is attributed to older people's contempt for younger generations). There's also a chance that it takes the same meaning as comedian, jester, etc. Basically, the "wags" are making fun of people who pay for books that they could get for free from the library. It's really hard to interpret writing sometimes because the writer's intention and my understanding can be completely different. Sorry I can't help you more.

I am certain Peachey and Amanda are correct. I'd add this. This meaning of "wag" is not core English vocabulary. It's good to UNDERSTAND, but you don't need to learn to USE it. It is somewhat literary and old-fashioned. A phrase like "wags have said" refers to a quip or wisecrack that is "going the rounds" and being repeated. It means "I can't tell you who said it first. Everyone who want to appear witty is repeating it." Here are some examples of use. "Clever wags have said that the world's Golden Rule is 'Whoever has the gold rules.'" "Some wags have said this building, with its diamond-shape top, looks like a giant pencil sharpener." "As some wags have said, a CFO risks going from pinstripes to prison stripes through the release of a fraudulent financial report." "Because of its reputation for high taxes, wags call the state of Massachusetts 'Taxachusetts.'"

Hi In the uk itwags/wag has a slightly different meaning, and refers to famous or well known women, they are in the news and like to share their opinion on things or people like to follow them here is a definition but it also now just mean any woman, women (usually, but now even men can be a wag!) WAGs (or Wags) is an acronym used to refer to wives and girlfriends of high-profile sportsmen. The term may also be used in the singular form, "WAG", to refer to a specific female partner. The term was first used by the British tabloid press to refer to the wives and girlfriends of high-profile footballers, originally the England national football team. It came into common use during the 2006 FIFA World Cup, although the term had been used occasionally before that. The acronym has since been used by the media in other countries to describe the female partners of sportsmen in general.