Considering the kind of boats pirates are likely to possess a seastead militia could likely provide equivalent localized protection. Naval vessels are expensive

Considering the kind of boats pirates are likely to possess a seastead militia could likely provide equivalent localized protection. Naval vessels are expensive b/c of the scale of battle they are fighting. Less than a millions dollars or so of equipment and a few dozen militia would be enough to repel any pirate incursion to date. Pirates are in it for the money, they aren't going to be willing to accept large casualties.