It's also nowhere near that cheap.

McD is hella expensive, especially if you have to live of of it.

A 8-10€ basic menu is good to fill in a single meal, but while having a ton of calories, doesn't satiate enough to count even as a full meal (which is on purpose so you order more). At my local prices, you're looking at 13-15€ minimum, to have a satiating meal out of McDonnalds.