That’s not cheaper. Run the numbers and you’ll see. Solar by itself is indeed pretty cheap per kWh if you don’t care about matching supply with demand, but storage very much is not. If it was, you’d see investors build standalone storage, to buy cheap electricity, store it, and resell when demand goes up. This is not what’s happening: instead, existing projects are based either on heavy government subsidies, or on vanity buyers, who want to pay above market prices to signal eco awareness, like Starbucks in one of your links.
The problem with running the numbers is that the actual numbers for nuclear are basically unknowable and most governments have given a taxpayer insurance that covers this unknown number "in blanco".
This means that most of the costs that will be caused by operating a nuclear power plant are not included in the costs of operations, and therefore not in the "price per MWh" or similar numbers. We don't know what this number is but we do know it's a very large number, and by removing it from the resposibility of the plant operators it represents a very large hidden subsidy for nuclear power.
Chernobyl and Fukushima are the familiar elephants in this particular room of course with he most recent estimate for Chernobyl passing 600bn usd in 2016 (and counting still of course and for the forseeable future) but I like to use the Asse II salt mine in Germany as a more digestable example.
This mine was used to store nuclear waste in the 70s which turned out to be a very bad mistake that has to be fixed in the coming few decades. The cost of this project, (estimated to be at least several bn euros) is not added to the cost of nuclear, it's just charged to the current taxpayers. The power plants that generated the waste stored in this mine are closed long ago but they keep costing money decades later.
Nuclear seems cheap because we're paying for it with credit cards issued to our grandchildren.
How much of that is just sensitivity to the cost of battery cells? If most of the world can buy lithium iron phosphate cells at $100 a kw/h, would battery storage be cost effective in ways it isn't at $300 a kw/h?
(I'm not sure what the actually LFP cell wholesale costs are these days; I get the impression that historically they've been a lot cheaper in China due to patents, but the last of the major patents expired about a month ago so maybe low cost cells will show up everywhere if production can keep up with demand. As a retail customer though in the U.S. it's really hard to find anything under about $300 a kw/h -- if utilities are paying a similar price, I can understand them not wanting to go all-in on battery storage. There's no reason for them to continue to be that expensive.)