There is some precedence to take into consideration the financial situation of parents.
On Canlii, most shared custody arrangement are calculated as the net amount, but then the judge increases that by anywhere from 0% to 50%. The judges say that this is to take into consideration the fact that the table amount is for full custody, and when it's shared custody, the child has two homes, so double the expenses.
I haven't done much research on this, just read it while doing research on other topics.
But, for inequality in standard of living, it's usually taken care of with SS. And, if there's a big gap in income between the two parents, SS may be extended longer than the guidelines.