Many of the JDAMs shipped to Israel aren’t owned by Israel but by the United States. This is because, starting in 2009, the U.S. began storing weapons and military equipment in Israel. These emergency supplies serve a dual purpose. The primary purpose of this gear is to be quickly flown to American forces in the region in need of it. But the more likely use of this stuff is for Israeli troops, if Israel got involved in an intense war and needed rapid resupply. In this situation the United States could simply release the ammo and spare parts to Israel. Because of this dual purpose, all the weapons and spare parts in the warehouses and bunkers are material in use by both the U.S. and Israeli forces. Currently, there's nearly a billion dollars-worth of stuff in the emergency stores, which include JDAM bomb kits, missiles, other ammunition, spare parts, armored vehicles, and electronic equipment.
Israel does not have to buy JDAM from the United States because Israeli firms have developed similar gear. Five years ago an Israeli firm developed a variation on the JDAM called SPICE (Stand-Off Precision Guidance Munition). SPICE adds a camera in the nose, where you can store several digital photos of the target (a building, radar antennae, or a moving target, like a missile transporter). When SPICE gets close enough to see what's down there, it's guidance camera compares what it sees in front of it with what is stored in its memory. If it gets a match, it heads right for it. If no target can be found, SPICE hits a specific GPS location or just self-destructs. SPICE equipped bombs can be dropped up to 60 kilometers from the target. SPICE costs about twice as much as JDAM kits and is similar to earlier (pre-JDAM), and much more expensive, U.S. smart bomb designs.
Israel prefers to buy JDAM mainly because of the lower cost and partly because Israel gets over a billion dollars-worth of military aid each year, and most of it must be spent on American made ammo, equipment, or weapons.