A $150,000 salary in Seattle might equate to roughly $115,000-$125,000 in Austin, but use a cost of living calculator to confirm. Housing is significantly cheaper in Austin, but factor in property taxes if you're buying. Texas has no state income tax, which is a plus, but property taxes can offset some of those savings. Consider commute costs too; factor in traffic patterns in both cities when calculating your overall expenses.
budgetliving: Don't forget about the heat in Austin; those summer AC bills can really add up, offsetting some of the income tax savings, especially if you prefer keeping your house cool.