Remember that peak power is much more valuable than non-peak power (in some places non-peak renewable power has a negative value) so buying it at a discount, wasting most of it in the process, and selling it at peak time can still be economical.
BTW one solution is to use existing hydro dams as partners to wind/solar, add extra generation capacity to the dams, share the transmission infrastructure between the wind/solar/hydro and simply let the dams fill when the wind blows/sun shines. That's more efficient than pumped storage