Open resource monitor. Why in the world would the game use that much? Simple ajax refresh should use mere bytes...
Just checked it myself and it's used about 1.6Mbps. I suppose it's because it's transfer full state of all games in list with every request and it's likely load server-side less than make multiple queries.
face it, the ui is the worst part of the game. Lobby is extremely laggy, and if you open game options while ingame, your pc will nearly crash... at least for me and all other people i talk with it is like this.
Not sure how this your post related to bandwidth usage. Games list and details update might be implemented any way Uber want to and most likely at moment it's updated this way to minimize load on master server. E.g master server only need to push static game list update like once second, but then this static data is shared for all players. In many other games game client forced to connect each server to get full information about game state and I doubt it's any better than current way it's work. Considering PA itself use tons of bandwidth anyway I don't see why same 1-3Mbps usage in games list is a problem. It's completely unrelated problem and it's just way it's implemented at moment. Uber can make options screen lag-less once they have time on that.
It poll the game list every seconds, and filters are applied client side. Currently seeing only 7 games "in lobby", for 115 games in the unfiltered array.