> the SRBs could be reused although due to how cheap they were it was easier to just build new ones.

There is no official accounting or source from NASA about the SRBs complete costs, which are very difficult to quantify because of the large nature of the program. NASA said they were potentially cheaper because of the frequency of launches (which was never substantiated). No group has ever released a source or study accurately accounting for all costs.

What we do know, is dumping metal into a salty ocean damages them almost instantly. There is a reason SpaceX lands their engines on dry platforms.