The phrase "comparison sake" means making a comparison or looking at something in relation to something else. It is used to understand or evaluate things by comparing them. Full definition
For comparisons sake about how much is your family's total expenses during a year or a month on average? (marriagekidsandmoney.com)
And just for comparisons sake, that's only two more appearances than he had all of last season. (blackwhitereadallover.com)
Kylie will likely never live on a farm (she will probably own one at one point I am sure) because that isn't the life she will ever have, just as I will never own a Barbie pink Bentley no matter how much I want one (I don't, but for comparisons sake let's say so). (refinery29.com)