However, you're not making a free speech claim, and that is the basis for the decision.
3% is "obscene" as soon as there's someone willing to provide the same service for less than 3%, and not before. If you think that Apple or Google are going to really introduce competition into this arena, you haven't been paying much attention. Both of these companies have atrocious records of illegal price fixing in every market they've ever entered.
If the merchant looks at their transaction records, it will show as a Visa or Mastercard (etc) as having been recorded and processed. And most processors count ‘easy pay’ type NFC transactions as being equal to a ‘card swipe’ vs a hand entered number on the keypad.
I don’t need to be a counselor to have an informed reasoned opinion on the constitutionality of a law. I was responding to your comment wherein you said that the state can regulate commerce inside its borders and that the federal court needed to butt out. As you have, I could think of other ways to argue it too. For example, the transmission of the credit card data either in the air or over copper/cable/fiber is regulated too. I am not advocating either way just saying.
As for the question of free speech, CA merchants were not permitted to charge more for credit card transaction, but were only permitted to promote a discount to cash paying customers. This is mathematically equivalent so its not a question of deception, fraud, etc. Question was can the state regulate the way merchants communicate this dual pricing? The court said California may not restrict the free speech of a merchant by proscribing some of the ways in which he informs customers about the difference between cash and credit card prices. As a person who plays an attorney on the internet (/s), I think that is a fair decision and agree on these grounds.
Finally, yes I believe paying 3% (or being charged 3% either way you choose to look at it) is an obscene amount of money for a transaction. It is ironic in many ways the methods that cost banks the least cost us the most. ATM transaction, automatic pin swipes etc have much less risk, human involvement and time & overhead costs than checks or cash transaction yet they cost more “for the convenience”. And its not just 3% there is a flat transaction fee plus a vig (though some are lower, in the 2% range). Whether Apple or Google et al fees are reasonable is a separate question, I mentioned them by name in a series of names because they are well known upstarts but so far they are using many of the same systems. The point I was making was there is a dearth of competition somewhere in that market. You may be right that new comers are charging a lot of money too, but that would be because they can. And that would be the reason they are coming into the market in the first place. It if was efficient and competitive they would have much less incentive to enter the market unless they made it more efficient and could profit by that. If they are truly competitors and if the costs were transparent it should work to drive down prices over time and that would inhibit competition. But I think perhaps these companies are looking to change behaviors entirely, to switch people away from Visa/MC/Amex/Discover and into their own banking systems either as a bridge to their bank accounts or by offering credit terms of their own. Apple surely has the cash to open a credit division.