How much worse would it be to call an entry point 100x vs calling a bulk operation entry point with a list[0-99] 1x?
Short answer is : too much.
10000 gas per call minimum https://gitlab.com/morley-framework/morley/-/blob/1f4ad392173a49752f1326a9dd4a4d5b7f6c5e70/docs/gasConsumption.md with a limit per transaction around 1000000.
EDIT: after precision by Raphael, the minimal cost is 1000 gas and not 10000 as it used to be the case. It means 100 iterations are sometimes possible but it doesn’t change the general point: don’t do it in general, it’s still very expensive.