Doesn't change the fact that it's bleeding money from your country as your enemies (Egypt, Iran, Syria etc.) are feeding Hizbollah with currency to build the crude weapons.
All wars cost money. In the case of Iron Dome, the system actually saves money to Israel - shooting down a rocket headed to an urban area is cheaper than letting it hit.
First, not all rockets are intercepted. 4,594 rockets were fired, but less than 800 rockets were intercepted. The others, the large majority, were allowed to fall since it was calculated that they will not hit anything of value - usually fields or open areas. The system is very accurate in predicting the trajectory of the rockets.
This just hit me: 188 of the rockets fired from Gaza fell on Gaza and probably did more damage in that dense urban area than the 4,406 rockets that made it into Israel - oh, the irony!
Second, if a rocket hits an urban area, the government has to pay for the damage to private property, as well as for fixing the infrastructure. One destroyed building will cost more than many Iron Dome interceptors. Wounded civilians cost the country a lot of money as well.
Third, and this is more on the hypothetical level, had the rockets done serious damage or killed many Israeli civilians, Israel would have had no choice but to go into Gaza with brutal force to secure the ground and stop the rockets. Iron Dome is what allowed Israel to fight this as a low intensity war with a very limited ground action (that went in to destry the tunnels rather than stop the rockets) and almost "ignore" the rockets. A large scale operation would have cost an order of magnitude more than what this action did.