I think debt is also useful for the interest metaphor. An unfinished kludge by itself may not be very expensive to fix up and change, but if that kludge doesn't

I think debt is also useful for the interest metaphor. An unfinished kludge by itself may not be very expensive to fix up and change, but if that kludge doesn't change and becomes a dependency in a complex environment it is likely to become much more painful to fix later.