In Tanzania specifically, the $100s were fine. The weird pricing seemed driven partly by perception. It was usually street vendors who would say $1 bills were worth 2000 shillings (~84 cents), while the larger banknotes were fine. Other vendors would charge X shillings or Y dollars, and when you did the calculation, it would be about 70 cents per dollar. I had crisp $1 bills and asked them why they discounted $1 bills so much? And some responded they were easy to counterfeit. There was also something about banks not taking pre-2009 (if I remember correctly) dollars, and sometimes they may not be bothered to check the dates.

But even at exchanges, the bid for $50s was beating the ask for $1s, I was thinking there's a trivial arbitrage opportunity haha.