The issuing banks have teams of people who are very smart, have extremely accurate data down to the individual transaction, access to the computers to crunch th

The issuing banks have teams of people who are very smart, have extremely accurate data down to the individual transaction, access to the computers to crunch that data appropriately, and spend their (working) lives on this topic. You are a dude doing this in their spare time as a hobby, with access only to your own set of data and not even the full set of that (e.g. you don't see the interchange fees etc.) I suspect that the bank is winning much more than you think on your business, even if you are getting a good reward. They are getting other people to pay them even more than they are paying you. Maximizing credit card reward can be a hobby that leads to minor ROI- like investing in individual stocks it might be lucrative and if you enjoy it more than golf definitely pursue it. But don't think you are fleecing Bank of America or Chase or whomever.