I see, Apple is giving the same price for iPhone 15 for all 3 carriers.
But if you check 14/13/SE, then if you do not chose Verizon, the price is $30 higher. I bought a 13 mini yesterday morning, which is when I experienced the extra $30, and I assumed it applies to all the iPhones.
Apparently, current year iPhones are excluded from the $30 surcharge for non Verizon subscribers.
Also, all iPhones sold on apple.com are unlocked, even the $799 ones. Only exception is if you buy with an ATT subsidized contract.