Theoretically, if power-to-gas plants can be manufactured at scale, you could make gas generation plants further away from where energy is being consumed. We already have tons of infrastructure on this planet for moving gasoline around.

You could also keep ICE engines in use without worrying about their carbon footprint. Excess renewable power turns into fuel to be used in cars, boats, trains (diesel electric freight cars), and airplanes.

Using this tech for off peak leveling on the grid might not be cost effective, but it can certainly be used to support the existing infrastructure we have to allow for a more graceful transitional period.

Will the cost stay high in a large scale production?

I have never seen an estimate on that, or a plant design detailed enough for extrapolating it. Do you know how those plants are built?