How much does a swarm of extremely long range jet ski robots with hardened military electronics and large explosives packages cost?
Getting enough of anything that can do serious damage to a ship to overwhelm the defenses is going to be an expensive undertaking. Maybe if some idiot sails a $10 billion aircraft carrier close to shore such a mass attack is justified, but it is simply not at all evident that "some success engaging Russian surface warships" equates to posing a serious threat to modern navies.
Getting enough of anything that can do serious damage to a ship to overwhelm the defenses is going to be an expensive undertaking. Maybe if some idiot sails a $10 billion aircraft carrier close to shore such a mass attack is justified, but it is simply not at all evident that "some success engaging Russian surface warships" equates to posing a serious threat to modern navies.