Israel is not "reselling" American technology (well atleast not in this case).The PHALCON is an Israeli system which has a number of American sub-systems.Which is the case with many weapon systems now.
About taking bids with from everyone,well the best way to get a good bargain is to promote competition even if it is skewed in nature.
In any event, with the amount of US aid Israel gets, I'm not comfortable with them using their US-subsidized position to undercut US companies