1.'Replace' is a PM action; the item still has some useful life left at the time of PM
2. Useful metal or other materials may be recovered from the scrapped part, but there are energy and other processing costs
3. 'Repair' generally needs more skill than 'replace'. In time the skills may be lost due to lack of use when 'replace' becomes the preferred option
The 'economic' model does not take these into account. Only the measurable and opportunity costs are considered
On the flip side though, 'replace' decisions keep the economy active, jobs secure and everybody happy. Will it keep the economy competitive?