"Cheap". The logic board is the main component of the device and it is expensive. If you have water damage, send your phone to an authorised repair shop(out of warranty replacement) or a third party(if you want your data back). To update your storage, there are specific people you can go to or mail them your device. Logic board replacements do not exist, all you can is extract it from another iPhone. Try searching eBay or aliexpress.
The only way to fix this is to buy a new fpc connector and resolder it with micro soldering equipment. If you have ripped pads, it will add to the time and price. Also a logic board repair will cost you somewhere between $150 to around $350.