Ilovepizza is right: the FICO scoring formula is rather insensitive to changes in the balances on installment loans like mortgages. And yes, astonishing as it might seem, if you're carrying $900 worth of credit card debt on three cards with a combined limit of $1000, paying $800 would likely raise your score 50 to 70 points or so.
Paying $600 thousand on two jumbo mortgages totaling one million dollars might get you 5 to 10 points. Bizarre? Illogical? Perhaps. But that's how the system works...