I know technical debt is a metaphor from finance and this question is kind of philosophical.
How would you define the interest rate of technical debt and especially differentiate it from the underlying loan?
Example: Due to a close deadline, the team takes a quick and dirty shortcut and takes technical debt. It gets paid back pretty soon by refactoring to a clean solution. The effort for building the clean solution is the loan while the additional effort for the refactoring as such + the potentially lower productivity of dealing with the code of the dirty solution is the interest, right?