You can argue safety (bonds you have sovereign default risk vs cash will have bank credit risk) but your math is not incorporating how a transaction in this cas

You can argue safety (bonds you have sovereign default risk vs cash will have bank credit risk) but your math is not incorporating how a transaction in this case would actually take place. It's not as simple as just holding onto $100. You have a deposit rate of -0.40% at the ECB. So instead of -0.40%, you settle for -0.14% which is what these newly issued Bunds are yielding.