Red Frog Events, a Chicago-based events company, has a tree house in the office. (This isn’t it.)

It cost a cool 100 grand.

There’s also a zip line and a conference table made entirely out of LEGO bricks.

CEO Joe Reynolds says that this was totally worth the cost. It’s not just because of the fact that happy employees are more productive ones or that all you have to say at a job fair is “We have a tree house” and the resumes will begin rolling in.

It’s also a way to show mutual appreciation.

Fistful of Talent blogger Marisa Keegan expands on the thought.

“It’s hard work creating an office space this crazy but the companies that pull it off understand that being over-the-top sends a very clear message to their current and future employees. By saying nothing at all, the sheer magnitude of the office space screams, ‘Look at how much I’m willing to invest in creating an awesome work environment. If you think this is over-the-top imagine how much time and money I’m willing to invest in you.’”

And yes, it’s a pretty cool treehouse. You can see the photo here. Dogfish Head brewery in Delaware also has a (smaller, outdoor) treehouse for meetings. And Austin, Tx-based ad firm Smiley Media boasts an indoor nest and (not pictured) a conference room with a secret door.

And we don’t have to go into the perks offered at places like Google and Microsoft, surely.