Let's say a F-15 costs X Dollars, and it's effectiveness in a war is 100 'units.'
Let's assume Israel can build a plane that costs X+Y Dollars (more expensive than the F-15), and that has an effectiveness of 115 units (more 'effective' than the F-15, and whether by effective I mean in terms of combat, or ease of maintenance, or specific viability to the mission set Israel would use it for, really doesn't matter here ...just that it is more effective but at greater cost).
Finally, let's assume that the nation states that are adjacent to Israel and could be threats have planes that have an effectiveness level of 75 units.
Under such a scenario, Israel will never develop its own planes. It can get a F-15, which is cheaper than any indigenous plane Israel could come up with, and still more effective than any enemy fighter (for a real like situation, look at the Japanese F-2 and compare it with a F-16. Slightly more capable, especially at the time since Vipers didn't have AESA radars then, but vastly more expensive). Throw in political considerations (eg pressure from the US for Israel not.to develop a F-16 competitor in THE LAVI) and budgetary considerations, and Israel will never produce a plane unfortunately.
“Never” is a large word.
There is much room for B-tier development of ground-strike aircraft akin to the A-10. They are not sexy and profit margins are thinner.
But there is a large market for them throughout the world and the US big boys are not particularly interested in such projects.
Of course, this is how Toyota got started.
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Cheap econo-boxes......