Undergraduate computer science student in Montreal. Probably more socialist than most people here.
I think economics is especially prone to this kind of "It's more complicated than that" issue. The idea that firms will reduce employment in response to higher minimum wage places a great deal of faith in the efficiency of markets. There are plenty of ways that an increased cost of labor wouldn't lead to lower demand: there might be resistance to firing employees because of social pressures; institutions may simply remain stuck in thinking that a certain number of people are necessary to do all the work that needs to be done, and be resistant to changing those attitudes. Consider the phenomenon of "bullshit jobs". If you've ever worked in an office, in the public or private sector, you've probably noticed that a huge number of employees seem to do little of substance. Even as someone who worked a minimum wage job in a department store, many of my co-workers seemed to do little if anything of use, and yet no effort was made to ensure that everyone was being productive.
If anything, I would argue that the idea that markets are, by default, perfectly efficient (or close to perfectly efficient) goes against the lived experience of me and the people I know, and my prior is to disbelieve arguments predicated on it, unless there is some specific evidence or particularly good reason to think that the market would be very efficient in a specific case (such as securities trading, where there are a huge number of smart, well-qualified people working very hard to exploit any inefficiencies to make absurd amounts of money)
So, I take issue with the implication that the FDA's process for approving the covid vaccine actually delays rollout or causes a significant number of deaths. From my understanding, pharma companies have been ramping up production since they determined their vaccines probably work. They aren't sitting around waiting for FDA approval. Furthermore, I think the approval process is important for ensuring that the public has faith in the vaccine, and that it's actually safe and effective.
Or you could just look at how much money goes to highly effective charities, since we're talking about abolishing fees for all donors, not just EAs. The AMF had donations totalling 36 million in FY2020, so, using your values of 2% credit card fees, 15.4% of money donated by credit card (though I suspect the real value to be much higher, especially when considering non-EA donors) and visa holding 50% of the credit card market, that's a total of 55'000$ for just one charity. Given that, I think it's perfectly reasonable to say that visa eliminating their fees would increase funding for the most effective charities by hundreds of thousands if not millions of dollars a year, though I disagree with JSWinchell's methodology