I don't want to be rude*, but 60k between two is not that much. I think the average UK salary is in the 31k range, so your joint salaries are average. I think Y travel is probably considered average travel given how many more seats there are in Y than in J or F. So I don't think it's really surprising that someone at that salary can't afford J travel.
*I say this as someone who also earns an average salary!
No offence taken, but are you referring to 60k net as a low salary in London? We are talking about 5k per month to spend after taxes, NI and pension has been deducted.