[improbable22]

No, I don't think fanzhang's point assumes infinite anything.

To give a more concrete example than GP's repair of an LCD, let's think about repainting a car. Doing this in your back yard like your grandfather might have done it certainly has much higher environmental costs than the original paint job. You'll spill paint-stripper on the grass. You'll buy two tins of paint and throw the leftovers away when you move house. You won't have the factory's precisely monitored spraying, and air filtration.

Of course the point of repairing is that it saves all the other parts (like the engine!) so the balance may well be positive. But we should not assume that any options are zero-cost.

[zeth___]

They are assuming that prices reflect the costs of the products. Externalities however are completely mispriced, so comparing the monetary value of buying new vs repairing is very misleading.