Hydrogen, can come from basically two sources. From some type of natural gas, or split from water, by electrolysis. We aready know what natural gas prices are doing. The price of hydrogen from natural gas will be dependant on that.
The other source is electrolysis. Here in the Pacific Northwest we have the advantage of having many hydroelectric dams on our many rivers to generate cheap electricty.
The dams do not generate enough electricty to supply the need we have now for electricty, we are burning natural gas to supplement the generation limits of the dams.
Switching motor vehicles over to hydrogen will not solve the problem. Instead of CO2 coming out of the exhaust pipe of a car, it will come out of an exhaust stack of a natural gas electric generating plant, if electrolysis is used.
Even if cars and trucks were converted to totally electric, we would still have to burn fossil fuels to make the electricty.
Wind power is an option, but many do not want those unsightly wind turbines in thier back yard, or in the area they might sail their boats off the coast of Massachusetts.
Solar cells are coming down in price, but they are still cost prohibitive, currently.