What do you mean by astronomical? My back-of-the-napkin estimate is that you'd pay about $8k a year in battery costs to supply a household ($20k 18kWh battery system lasting 5 years, then double it).
Obviously that's missing commercial power, utility-scale storage, heavy industry, electric vehicle charging, etc., but it seems like factoring those in would give you a big yet feasible cost, especially if storage gets cheaper over the next decades.
Here is 30kWh of LFP batteries for $9,000. Now that doesn't include the inverters or installation or anything but LFP batteries have excellent longevity, in this case 7000 cycles to 80% depth-of-discharge. That means charging and discharging the battery every day for 19 years and at that point, you still have 80% of the remaining capacity.
Obviously that's missing commercial power, utility-scale storage, heavy industry, electric vehicle charging, etc., but it seems like factoring those in would give you a big yet feasible cost, especially if storage gets cheaper over the next decades.