With interceptors that cost the defender $100k/unit and shaheds that cost the attacker $10k/unit, over time the attacker can bankrupt the defender if the target is something the defender cannot afford to lose. Sometimes it takes several interceptors to eliminate the threat. Therefore part of the focus in the design of interceptors is to keep their unit cost low. The unit cost of the first versions of shaheds may have been $10k; more recent models that fly higher, are equipped with a jet engine, more sophisticated electronics, cameras etc. are significantly more expensive. To the point it's not clear to me, of Ukraine or Russia, who pays the higher price during a mass attack at the moment.