Using the calculators at paycheckcity.com, $250k for a couple would translate into a net income of $164,800. $125,000 as a single translates into $79,700 net.
The married couples makes $85,000 net MORE than the single guy. The fixed costs like living and food are about the same or neglibily more. If the married couple has car loans then that may be an additional expense, and perhaps gas.
So, the couple’s fixed costs may increase 5 – 10% over a single but their available discretionary income skyrockets making them infact MUCH more wealthy.