“Cash” or “Money” is what you have before you start flying.
Once you start flying you think back to the days when you used to have disposable income.
What you have left AFTER paying for flying is now your disposable income.
If it’s more than £6.50 a month, you’re not really that keen on flying tbh.
There are millionaires on this forum and there are those of us on meagre incomes, yet when asked the question
“How much money does it cost to fly?” we all give the same answer
“all of it”