No idea which area of Tokyo you live at and what kind of food you like, but I've observed that here it costs less to eat out than make food at home. Personally I don't cook, but once in a while my husband feels like making something specific at home & seeing him buy the ingredients and the time he spends to make it + time to wash everything, it would've been cheaper to eat something else out.
We live in a very busy area full of places to eat, so I personally pick something for my dinner on my way back home from the ice rink and my husband does the same on his way back from work. We go to the supermarket every 2 weeks and buy lots of food ready to eat as well.
I used to order from Domino's once a week too, but haven't done so for a few weeks since I want my weigh to be back to below 50 kg.
It's harder if you don't live near a variety of food places and need to rely on delivery only.
Here it'd be foolish to order since I can go around in less than 2 minutes in any direction and choose between McDonald's, Burger King, Chinese, Indian etc.