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"I want your cashiers to buy them from me at the retail price!"It's not anywhere near that simple. Electric power prices change dramatically throughout the day. For example, even retail prices may more than double during peak hours, if you have time-of-day billing.
In some markets, peak demand is caused by day-time air conditioning during a few weeks in July or August. The extra generation capacity needed to cover that tiny window of time is idle the rest of the year. Those peak hours are very expensive, in real terms.
In a market with small amounts of solar, that solar is helping offset some of the most expensive electricity of the year. And I've seen power companies push their major clients to install solar so that the power companies can avoid large investments in new power generation and transmission capacity.
With net metering, power companies pay retail when wholesale electricity is most expensive. And they credit it back during the night, when wholesale power is cheaper. (The early evening window is trickier, and the hours of sunlight depend on latitude.)
But once solar capacity is sufficient to offset air conditioning, the numbers for the power company get a lot worse.
(Full disclosure: I signed a 10-year net metering contract which would barely break even in 12-15 years, in a market with little existing solar. The power company instituted separate grid fees a couple of years later, which substantially changed how the contract worked. And so my system will probably never pay for itself. Win some, lose some.)