So if I go to a car dealership and ask how much a car is, and the dealer says $30K. I say I would pay $28K. The dealer says "sure! sold!". By this logic I would be required to buy the car.
the one with more similarities would be that you would have asked the dealer to sell at $28k, the dealer says $30k and you say okay.
secondly the courts accept verbal contracts unless there is a statutory carveout for a specific kind of agreement, the courts require proof to rule which verbal contracts happen to lack. so if you did it over email, or did it through a broker's portal that says using it is a binding contract, then a court would have the proof, which is the logic of the actual case here.
In my opinion a more relevant analogy is: Car dealership approaches person and asks to buy their car for $2500. Person says “Naah, price is $50,000 bro”. Dealership says: “Sure”.
Here I believe it’s more clear that the person is in fact not obligated to part with their car unless they take the required additional step of agreeing to the purchase and finalising all documents.
The seller seems firmly within their rights to say, "Sorry, my counteroffer was good only for 15 minutes."
This might sound silly but market conditions change in minutes and events happen like earthquakes or 9/11. In the absence of an agreed term of expiration I see no reason why a counter is good for any longer than the seller feels like it. Though with written or implied terms it would be totally different (see real estate contract offers for examples).
Am I missing something?
Yes. What’s your point?