The global arms market is a strange place, especially when it involves US or European manufacturers.
If you want US military hardware, just forking over the cash doesn't quite cut it anymore, not even if you're a close ally. You get a lot of contractual obligations on how to use the hardware or who you can resell it to. Also, I don't know a single US arms deal in the last few years that actually resulted in any form of profit for the US contractor directly from the customer. The money was made from the US government.
"Cash and carry" works with russians or chinese hardware, but not with US or EU stuff.
Usually it seems the US basically does not sell arms, but gives them away for political leverage.
Austria did buy Black Hawks but the countersale proposals were so hefty the US got zero profit out of it.
Recently, it was a subsim headline that the landing ship India got from the US (a 20+ year old clunker) is forbidden to take part in combat operations.
I suppose the only country that can use US weapons without (or at least with the least) restrictions is Israel.
I suppose one reason most european countries "go european" is that this means full control over your weapons.
Germany still has to pay license fees for the source code of the software of the Patriot missile system and will enter similar obligations with the MEADS system.
I suppose restrictions for AMRAAM and Standard missiles are similar.
I've heard the greeks did go russian for their air defence for the simple reason that they want SAMs that work when the Turks attack, and do not get turned off because Turkey is more in favor with Washington than Greece.