They didn't see it coming, There is a video of a guy laughing at these rockets then a rocket landed near him. It shocked them and filled their souls with fear. As for the money loss, Palestine surely lost more, They have like 60 dead by now along with bunch of accommodation towers, hospitals and schools.
Each iron dome missile might cost $40,000 to $100,000 while each missile fired by hamas or whoever might cost $2,000. Much cheaper no matter the price tag.
Hamas beats them on cost effectiveness and volume.
Israel could adjust their strategy to compensate. A different defense suited to lower cost missile spam.