Pipelines are cheap because we already build a lot of them. We already use them to move multiple products. It’s a somewhat generic technology (which is very impressive, dont get me wrong).
I’d be interested to learn how the capex breaks down for the HVDC lines. Is it labor? Procurement? Those can both be optimized with scale. Expand the qualified workforce and incentivize competition among suppliers. If it’s raw material cost it might be a little harder. I imagine right of way costs are also quite a bit higher owing to the large footprint. But then once you acquire the RoW it stays there in perpetuity. Still, I bet my favorite hat that once you consider the externalities and conversion losses the transmission lines are a clear winner. The electrical grid really only causes fires when its neglected, whereas gas infrastructure leaks constantly.
Those transmission losses don’t have immediate health and environmental costs, though, and even discounting those there’ll be conversion losses on both ends if what we want to get out of it is usable electricity from renewables. Dont take my skepticism for poohpoohing btw, this kind of counterintuitive thinking is one of the more fascinating things about economics. Or maybe I just like to argue :P
I’ll look up the paper, this is an interesting topic.