I would argue Visa and Mastercard and payment processing at large as the top priority by far. It's crazy that we've given up control as a society of the only mechanisms for electronic payments in an increasingly cashless world to unregulated private entities who continue to jack up fees as often as they can get away with. Makes everything 3-5% more expensive. Ridiculous.
While it's true many merchants pay 1-3% in processing fees, many of the costs involved are real. Building the network, fraud, rewards to consumers, etc.
Visa's net income is roughly $11 billion a year[1], and they process roughly $11 trillion a year[2]. So their take is ~.1%, not 3-5%.
Note that this ignores that banks may make money off these transactions as well. May be better to look at Discover (the lender and the network) instead of Visa. But I'd think the total take from these companies is much closer to .1% than even 1%.
[1]https://finance.yahoo.com/quote/V/financials/
[2]https://usa.visa.com/dam/VCOM/download/corporate/media/visan...