The allowances are supposedly an extra 7 k per year however rate of exchange affects this. for example pre 9/11 the USD rate was something like 1.6 now it varies between 1.8-1.97 at one poent it was 2.08! This makes a lot of difference, and its not always possible to bring it all home as you have to eat, but yes you dont have to use all your allowances.
On average a 1 night stop is $170. And you would need to buy dinner, breakfast, lunch and maybe dinner again depending on departure time, many crew just eat 1 meal to stock up on food so they dont have to spend more of their allowances but it shouldnt have to be like that.
Besides we get 4 weeks leave a year, not to mention time of sick or time not being called out on standby. These times you live on your basic which is a struggle. I think allowances are not the issue, what most of us want are better salary so we can take our supposed paid leave and not be skint.