Obviously, until you have enough renewable generating capacity to charge your storage, you are not selling stored energy: you sold what you generated.
It is extremely disingenuous, not to say dishonest, to make up scenarios based on status quo when there is still very little renewable generation capacity.
I find equally disingenuous and dishonest to talk about pumped storage for renewables when they do not exist as a viable economical model.
If you want to blame the lack of renewable generation capacity then feel free to do so. Pumped storage could in theory, in the future, when the time is right, be cost effective. We don't know. We are not there yet. Its a financial model to be to be tested when and if we get there.
For now the financial model for existing pumped storage do not care about the purchasing price or selling price, or what kind of power it is being charged with.
What is this "financial model" you imagine?
Utilities will need storage, and will build whatever is cheapest. In some places that will be pumped hydro. End of story.
If you are wondering why a company need a financial viable model to operate on then I can't help you.
All the existing pumped storage facilities that I know of do not generate their profit from buying low and selling high. They generate profits by providing a service of balancing the grid for short duration so that when a power plant is ramping down, there is a equal force being provided as a service so that the grid doesn't break down. The period of ramping down/up need to be covered somehow, a cost that either the grid operator or the individual power plants need to pay for. The end customer who pays by the kw/h do not see this cost, and it is a very insignificant cost of the whole since it only occur at start and stop.
But I am happy to be proven wrong. Please give me that link of one that buy low and sell high. A commercial operated pumped storage that buy renewable energy when its low and sell when it is high can be scaled up to be used whenever the price difference between low and high is great enough. The cost of operation and investment just need to be low enough that the margin between low and high price points can support it.