Most games of 30-60 and above exist merely to feed off of one or two poor players. Before a bad player comes to the table, the good players get together and often take it fairly easy on each other waiting for the game to get going. The 15-30 and 20-40 games are usually 3 or 4 solid players, 3 or 4 players that have some idea but aren't long-term winners, and a couple that are the fish. As you go down in limits the players slowly work down the scale where the solid ones become more middling players and the middling players are closer to the live ones, but the house is increasing its relative take.