Israel doesn't have the money to develop their own 5th gen fighter. No one does, really.
I can understand the attitude of wanting Israel to buy US stuff, though. I mean, when you're handing out billions in aid, you sort of expect them to use that money right back, you know? Now if Israel simply paid outright for everything they had, I would look at it differently. Then it would be a case of do whatever is best for you, outright.
That's why I don't believe the UK or Oz or India should be pressured into buying US stuff. If they want it, fine, but they can go elsewhere too. After all, it's not like we're giving them anything for us to expect that in return. Want to buy Euro stuff? Russian? Whatever, your prerogative!