Let's use the same example of a hypothetical simple toaster -like device, and assume that you have a specific breakage where fixing it takes 20% of the effort required to make the device in the first place.

I'd say it's feasible that massproduction and automation brings up the efficiency so that this already means that producing the item takes less human hours than fixing the item even if it's easily openable and servicable.

Furthermore, even if you have a scenario where fixing an item takes 20% of the hours to build the item, it's feasible that the local repairperson in a first wold country costs more than 5 times per hour than the cheapest possible place in the world where the item was manufactured.

It is quite realistic that the efficiencies of the global mass production toolchain mean that repairing many types of items doesn't make practical sense no matter how serviceable they are.

A person manually soldering a single capacitor can reasonably cost more than the manufacturing of the entire circuit board and its components - and that's not caused by faulty design, but by the effect of scale and automation; it's not that repair is expensive but that replacements are dirt cheap.