There's a fallacy about free electricity that runs through this discussion and those assumptions. Tony Seba is a major purveyor of this nonsense.
First, electricity isn't free to manufacture even if the market isn't interesting in paying anything for it at a given time. If no one is paying a wind farm for it's electricity, it will feather its blades to reduce overall maintenance costs rather than let them spin for free. Ditto solar panels, although to a lesser extent. Why exactly will utility scale farms give away their product for nothing? They'll either get $10 per MWh or just not deliver anything. Cheap manufactured electricity, sure, but not free.
Second, that there is low cost electricity being manufactured somewhere doesn't mean that it will be delivered for free. Transmission, distribution and administration costs aren't free. The retail cost of electricity is the manufactured wholesale cost plus the T&D adders. Transmission operators and utilities won't deliver the electricity for free.
Third, electrolyzers are only about 8% of the cost case for synthetic fuels like ammonia. The balance of plant for the electrolyzer is 27 or so full commoditized components which aren't getting cheaper. The Haber Bosch pressure and heat reactor that creates ammonia isn't free. The full stack of capital costs is such that business cases that can't run them 60% or more of the time per year don't add up.
The electricity as noted won't be free. The capital equipment doesn't come from a box of Cracker Jacks. Everyone in the chain needs to make a profit or they'll exit the business.
Fantasies like Seba's of free electricity enabling free hydrogen derived products are just that, fantasies.
