I would say that, for a male athlete, 55"+ would be getting into what I would call "elite." From my experience, most D3 basketball or volleyball players and many halfway athletic guys from other sports (soccer players, outfielders, lacrosse mids) can get up on to a 40"+ box. This would be for "normal" sized guys in the 5'10" to 6'5" range and fairly skinny like most players in these sports tend to be. Most guys I've seen who are jumping a legit 30" standing vertical can hit a 50"+ box jump. My best is 58" from a stand at 6'3" 215.
Average high school male who plays a spot can do 30", that's where I usually would start people when they are training unless they are heavy or uncoordinated; then I would start on an 18" or 24" to get some practice and make sure things are safe.
For females, I would say 36" is "good." D1-level female volleyball players (excluding the 6'4"ish middle-hitter types who often aren't too athletic) can often go 40"+. I usually start high schoolers who are halfway athletic/coordinated on a 24" box and many of them will move up to a 30" fairly quickly with a little practice on the landing. Most of the middle school kids I work with start on an 18" box.
There is also definitely a skill to box jumping. I would bet that, with Hanley's strength numbers, if he spent a few weeks practicing them, he could hit 48". So sometimes this can throw you off as I have seen people with higher verts do lower box jumps than others due to limb lengths, lack of flexibility, general unsureness, etc.