A rough answer, plus the assumptions behind it — because your real number depends on your full financial picture.
Using an illustrative 6.75% 30-year rate and a 20% down payment ($150,000), a $750,000 home runs approximately $4,350–$4,450 per month for principal, interest, taxes and insurance (before any HOA dues).
Applying a typical 28%–36% housing-to-income guideline to that payment points to a gross income of roughly $147,000 to $190,000 per year, depending on your other debts and the specific loan program.
This price point is right around where many buyers cross from a standard conforming loan into jumbo territory, depending on the year's conforming loan limit — worth confirming before you shop.