Finland are also charging to repatriate their citizens so we are not alone in doing this. And yes, the Government has said that the money can be paid later if not available now.
As I see it there are 3 reasons for a Brit to be in Egypt:
1 There temporarily on business - can't see that any individual is going to suffer a financial loss getting home because their companies (quite possibly not even a UK company) will pick up the tab.
2 You live and work there - therefore probably not paying UK tax so why should the UK tax payer pay to get you home?
3 On holiday. Cost may possibly be covered by insurance. If not, then if you can afford a holiday in Egypt in these difficult times you can probably afford an extra Ã‚Â£300 to get home. Besides, you have to accept that going virtually anywhere abroad these days carries a certain degree of risk - if you don't want to accept that risk then don't go.