quick calculation comes to about a 45% tax rate for single in CA and 42.4% for married. So 50% is a small exaggeration, but it's definitely closer to reality than 30-35% underestimate.
Note that these numbers are likely the marginal tax rate, the tax rate that the very last dollar was taxed at. However, all of the income is not taxed at that rate. That is why the commenter above mentioned effective tax rate, which is the calculation of (total tax paid / total income).
Why would you guess when someone told you they calculated? For marroed filing jointly earning $450k, the marginal rate is 35% federal plus 2.35% Medicare tax plus 9.3% CA tax.
