GET OFF WITH **collocates with "smaller-than-expected penalty"
The drunk driver who killed two people GOT 25 years in prison.
(25 years is a normal, reasonable penalty for this crime)
The drunk driver who killed two people GOT OFF WITH a year in prison and a five year suspended license.
(One year is too lenient, not enough for this crime!)
When a speaker uses "get off with" they are signalling their opinion that the penalty is too light.
It's often used when someone in authority has the power to make a harsh penalty, but shows mercy.
I was speeding like crazy, policeman stopped me, I could have lost 3 points on my license and a $250 fine but the policeman LET ME OFF with just the fine.
I GOT OFF WITH just the fine.
**Someone offered a correction on my example above. My run on sentence was to convey MEANING, which I think I accomplished. Even though I'm an English teacher, I put accurate and clear meaning above unnecessarily complex grammar.
A good teacher tries to make complex things SIMPLER, not simple things complex.