the price of the hydrogen is gonna be close to the same as gasoline, oil/hydrogen companies are going to charge you to extract the hydrogen through the sea water, were not just gonna be able to put sea water into our cars.
the benefit is gonna be a completely renewable resource and NO MORE DEPENDENCE on oil, a non-renewable resource. we'll still use oil/gasoline for another 50 years or so, by then i think we will be on all alternative fuels, and the oil company's and oil producing nations will then shift their focus to emerging 3rd world countries to sell their oil.
but i think the major players (i.e. North America, Europe and Japan) will have moved on by then.