Yes, this is a modern tree house/play platform designed for a 9 year old and her friends.

How much roughly would this cost

Depending on a few things and considering this was built in Carmel Ca. Highlands, out of "A" Grade, Kiln dried furniture grade lumber and 3form acrylic panels ($5,500 alone) the budget range would be $18,000 - $26,000.

Granted there are similar materials that could be substituted to bring the range down to $8,000 - $12,000 or even less, again depending on material grades and design.