During most of last year prices in Europe were routinely over 300, 400 even occasionally over 1000 per MWh because there was an energy shortage. At the same time the prices can easily go negative if the conditions are favorable for renewables. It's not crazy to think that you would be paid to charge your car when there is an excess and then get paid a lot when there is a shortage. I don't know who would say no to this deal.
My point is mainly that there are plenty of options available to stabilize grid prices that are way cheaper than using EV's. Europes energy crisis is temporary, over time the price fluctuations will go down.
That's actually not true. Let's say your calculation of ~100 per MWh for batteries is correct, we've seen that the wholesale prices were a multiple of that basically this whole year. Nuclear is above that price. I don't think anybody is seriously planning to use car batteries as the backbone of the grid, but as one of the last resorts yes. It makes sense for everybody.
Isn't that the big question? Whoever is confident that they have correct answer to that question should invest any coin they can get their hand on right this second.
Purely from a theoretical perspective, anything that can generate power at lower prices than the current market rate will be financially viable. With this past winters prices in Europe, it means literally anything. Even at times a diesel generator from your local hardware store would be a good idea (~.60 EUR per kWh).
But these prices won't last, in a few years we will be already back down to manageable price fluctuations.
It's pretty easy to see though that if battery based grid storage is going to be a big thing, it is not going to be EV batteries. The chemistry used in them is not optimized for life cycles (at least currently). LFP chemistry batteris that are in some Teslas has bettery cycle duration. Sodium Ion batteries will most likely be the choice for grid-scale deployment if they can be commercialized.
Of course at some point in the future if a lot of people with EVs say yes to this deal, the price range will narrow significantly, and eventually stabilize to the point where it's only just profitable given battery degradation costs. But it may take a long time to get to that stage.
