Early Access Game was $15 when it was first released, now it is free to play.
Unsure if they are changing the price to back to $15 when it launches. It does not look like any micro-transactions are offered.
Details: Darwin Project takes place in a dystopian post-apocalyptic landscape in the Northern Canadian Rockies. As preparation for an impending Ice Age, a new project, half science experiment half live-entertainment, is launched. It's called "Darwin Project" and it challenges 10 participants to survive the cold and fight to the death in a treacherous arena.