It’s tricky in some cases, but consumer electronics are actually pretty easy because most of the harm done is during manufacture (Apple estimates that more than 75% of an iPhone’s emissions come from manufacture). You could either expect Apple to pay for the externalities at production, or mandate that they’re required to accept back all dead Apple electronics and recycle them at a specific standard.

Even assuming that CO2 is the only relevant externality here (and not, say, electronic waste, mining runoff, chemicals used during manufacturing...), we don't have accurate models that can tell you a dollar cost per ton CO2. Estimates I've seen range from "climate change is not real" to 600 Euros.

On the other hand you only have to disassemble an iPhone and check the availability of replacement parts to see whether it's repairable or not. It's easy to say exactly what damage can be repaired and what not. Very little room for discussion.

But as consumer devices become miniaturized and waterproofed, these kinds of advances come into natural tension with ease of repair. They are also the keys of somebody's data kingdom, and external repair shops bring in some risk.