Re: Banking isn't really a highly computational process
You're many orders of magnitude wrong in your assessment of the computation power required.
Payment systems are incredibly complex and there are many layers, from the merchant, to the terminal, the merchant acquirer, the scheme provider etc....
Those 1300 card transactions per second probably equate to over 50,000 transactions at the data/message/API layers at least and that's just at the scheme end, and because it's payments, everything is logged up the ying yang.
Source: I build platforms for payment providers.