"I’ll take a stab... Cash rate .75% Mortgage rate 4.5% Gross...

"I’ll take a stab...
Cash rate .75%
Mortgage rate 4.5%
Gross Margin 3.75% (or 5 x cash rate)"

Thanks.
OK, that makes sense.

But, in that case, I wonder who pays the wages of, for example , CBA's 50,000 employees?
And the rent for all CBA's branches around the country?
And for all the computers and office furniture, and all those ATMS?
And the telephone and electricity bills?
And...
And...
And...

What, I wonder, is the margin after all of those aforementioned expenses are deducted?

.