When last season ended I suggested, that you get a finish bonus for the spot you finish in. One time income for everyone depending on the ending spot, with playoff games adding 0 income.
Second option would be to give relegation matches, scrimmage attendance. That would remove most of the income.
From another point of view, isn't relegation income giving lower tier teams some needed boost to catch up a little. We can all agree that nr1 and nr2 teams in conference have it good. If they actually deserve their spots, they will get decent income from playoffs. 3-4 will prolly get less than 6-7. You should avoid 5,8. Now depending on league strenght sometimes 5-th or above is heaven -> those being divI-s in most countrys.