oh, this.
i'v spent ages trying to find decent bulk prices for fish and imo, they are simply not to be found on the internet - serious, to-factory or to-catering prices are simply not advertised to the public, as doing so would lead to a self-destructing spiral of lowering prices.
your best bet to find lower priced fish is to go to a supplier's fish market .. they are hard to find, and might not be open to the public though, depends on where you live. small fishing towns outside of metropolitan centres will also probably have people you can contact for good deal, though everywhere is getting harder to find independents, as most catches are owned by companies and they sell on contract.