I'd opine that about 8-10 teams have a realistic shot. Some lower ranked teams have some finite percentage, but it's single digit if that. In most seasons, about five teams are roughly the same, each can beat the other about half the time. They are followed by five more that are competitive, but maybe would beat the top five 30% of the time.
If you run percentages, obviously a team's chances of winning a playoff decline as playoffs involve more and more games. The "best team" might have an 80% chance of winning round one, 70% in round two, and 60% in round three. Collectively those are not very good odds (about 1 in 3).
