Is it worth generating methane from electricity instead of hydrogen? Sabatier reaction etc?
If this infrastructure is built out, it may also provide the path to pulling CO2 out of the atmosphere or ocean and permanently sequestering it. That is something that I think we'll probably be very interested in doing in coming decades. Having affordable technology for that (perhaps $20-80/ton?) would enable CO2 emissions for those cases that really require it, and possibly also some clawing back of the worst parts of anthropogenic climate change.