It seems to me that its not what teams actually make it to the playoffs and the series, but after a small market team has a big year, the players stock goes way up. The following year they can no longer afford many of the players contracts that got them there the previous year. Most of the larger market teams get into a playoff streak and stay competitive for a number of years while the low budget teams usually have one "spike on the graph" then drop right back down for a longer time.