The site is exactly what you’d expect — a place to buy and sell 3D models. Because the official 3D Warehouse doesn’t allow you to sell models, they decided to create a way for people to do that.
In their words:
"That is why we created Geo3D Market it is for all SketchUp 3D modeling lovers! This concept was created especially for architects, designers and geographers. The model should be a representation of a building/structure/object that exists, has existed or will exist in the surface of Planet Earth.
Modelers can sell their models, fast and easy! Geo3D Market has a price system based in levels, for now: $4.99, $49.99 and $99.99. Nobody knows better than modelers how much their models worth."