Person X produced me $A amount in 40 hours. His salary is $B. B being much smaller than A[1], I can increase it without much an impact on the bottom-line. But, again, B being much smaller than A, if he worked less hours, I'd reduce A much more than I reduce B.
[1] It has to be, otherwise, will all the overhead a business has, I'd go broke.
Person X produced me $A amount in 40 hours. His salary is $B. B being much smaller than A[1], I can increase it without much an impact on the bottom-line. But, again, B being much smaller than A, if he worked less hours, I'd reduce A much more than I reduce B.
[1] It has to be, otherwise, will all the overhead a business has, I'd go broke.