The cheaper replacement can make the original impossible to afford repairing.

Repair competes with replacement. Once a new one costs less than the labour to fix the old, fixing becomes a luxury, and the good object you already own becomes uneconomic to maintain. Cheapness in the market removes the option of keeping what you have, which is a strange kind of loss.

Where something is worth repairing, the calculation should include how long each will last rather than only the price today. Learning one basic repair yourself changes the arithmetic considerably. And it is worth noticing when the choice has been made for you by the price of the alternative.