It's very high.
In 2014/15, Ipswich finished 6th with 78 points. Wolves missed out with 78 points and Derby had 77 in 8th!!
In 2016/17, Fulham finished 6th with 80 points, 5 points above Leeds. That's the highest points total for the Championship.
Across the 3 lower divisions, 82 points for finishing 6th was achieved by Stoke in 1999/2000. We finished 6th in our playoff winning season of 2002/03 with 81 points.
The average since the advent of the playoffs is 73.6 points. Prior to the advent of the playoffs, using the iffy method of awarding 3 points for a win, the average points for finishing 6th was 65.6. That was with only 42 games a season, though. Pre playoffs, the side finishing 6th had won 1.56 points a game. Since the playoffs it is 1.6 points a game, but draws were more commonplace when there were only 2 points for a win.