A wire has no such limitation and can be practically "instant" with same-day settlement if you send it early enough. A wire usually comes with some hefty fees

A wire has no such limitation and can be practically "instant" with same-day settlement if you send it early enough. A wire usually comes with some hefty fees and as you point out, it is restricted to "banker's hours". FedNow transactions are fully automated and designed to work instantly 24/7/365. The cost to banks will be a few pennies each to support the system operation. Banks being banks, some will probably try to add a fee for this initially but I expect competition will quickly reduce this to zero. Debit card transactions are typically "free" now but the real cost to banks is actually more than what a FedNow transaction is supposed to be.