Why is staying single cheaper? My girlfriend and I save a lot of money by being able to share an apartment and splitting the rent, internet connection etc. Living alone would be much more expensive for each of us.
..and like someone mentioned their 200$ food budget, try spending twice that amount on kindergarden a month that your kid is not attending for now because he's home sick and you're spending extra on treatment.
When you've exhausted your saving options, making more is still the best option for saving money:) Simple math, if you spend 3000/month of your favourite currency, then you'll have twice more money by earning 4000 vs 3500.