There is absolutely a rational difference between 30 and 50%.
The numbers are clearly different, but not in the "one is slavery and the other is not" kind of way right?
We as a society went to war with companies over how much time they can require of us. Nowadays companies can only require us to work roughly 23% of the hours in a week.
50% is 84 hours/week, we as a society have already deemed the difference between those to be significant enough to fight about.
The difference between 50% of your income and 30% of your income is significant.
There isn't a rational difference between 30 and 50, the only difference is "I feel that it is too much", right?