You could put 1 player in the lineup and forfeit, but that isn't very nice to the team you are playing as it messes up their minutes. You can easily spend 3k and buy 3 scrubs from the transfer list, put them in the lineup and then fire them after the game.
Injured players will still receive training if you are training stamina, free throw or gameshape.
In the playoffs you still pay for scouting, you still pay for staff salaries, you still pay for player salaries, you still receive tv contract, you still receive merchandise. But for arena income, you get 66% of the arena income for the playoff match if you are the home team, and you get 33% of the arena income for the playoff match if you are the away team.