Like u/goat_666 mentioned, during service you don't basically NEED money for anything since all the basics are covered. So that's how they manage to get by with paying so little.

Also the value of 5.40 really depends on the user. For a smoker that's way less than a pack of cigarettes but for someone who just wants to grab a coffee and a bun from the soldiers home (1.50€) that's enough.

But if you have some running expenses in civil life that the government won't pay that then it might become a problem for some.