Item selling price: 10000
Deposit required to place item on GTN for 10000 = 600
deposit is not based on selling price but on the item value (if i understand the patch notes correctly).
so maybe the tax didn't change (i was not aware that there was a tax before 1.5) but it's % is higher than the deposit and that is why the overall income is lower than before.
so the income in this example would be: 10000 + deposit - tax, where tax > deposit