Is free to play really free?

Have you ever stopped to consider the true cost of so-called 'free-to-play' games? While it may seem like you're not paying anything upfront, are you really not paying anything at all? From in-game purchases to the potential impact on your time and productivity, could there be hidden expenses lurking beneath the surface? Is the freedom to play really as free as it seems, or is there more to the story than meets the eye?