Value and outcomes
Cost of change
Also called1:5:30 rule, Cost of fixing defects, 1:10:100 rule
The idea that a problem costs more to fix the later it is found: little in design, more in development and most after release.
The intuition is sound. Changing a sketch takes minutes; changing shipped code means rework, testing, release and sometimes data migration, plus the cost to the customers who hit the problem first.
The version usually cited in UX writing is roughly $1 to fix in design, $5 in development and $30 after release, attributed to Forrester. The primary report is not public, so treat the shape as more reliable than the exact multipliers.
Common mistake
Using the '100 times more expensive' version. It is usually credited to an 'IBM Systems Sciences Institute' study that nobody citing it has been able to produce.