The cost of disposal varies by where it is disposed, not where it is purchased or made. It makes no sense to add an arbitrary cost to a product when the receiver of that money is not the one dealing with the externality in the first place.
The same goes for carbon emissions; a properly managed landfill that captures released methane is in fact a method of carbon sequestration. Adding a carbon tax would merely create a new slush fund or dump into an existing one.
Proposals to add cost to disposal are meant to correct for these distortions - to really represent the collective cost to the world. This absolutely should not be done arbitrarily - massive, ongoing research should be done to ensure its correcting for these distortions appropriately. Rinse and repeat for fossil fuels.
BTW, a methane-capturing landfill is, at best, carbon neutral, not sequestering.
As for landfills being cheap, that isn't a bad thing. That means the externalities at those sites are low. I live near an old one that was turned into a 50 acre prairie restoration space with about 2 miles of walking paths and full of wildlife. As others pointed out, burying carbon does sequester it. Methane capture merely prevents it from getting back out when it is nutrient and water dense (aka food waste).
2. Assuming that certain places have lower externalities doesn’t make sense. Aside from the global footprint of trash in general, there have been tons of rehabilitated sites but they will need maintenance and monitoring for hundreds years.
> As for landfills being cheap, that isn't a bad thing. That means the externalities at those sites are low.
No, that means that most of the actual price is not accounted for and is dumped on the public instead.
> Often the choices made by "the individual" don't account for externalities that aren't built into the price...
You put "the individual" in quotes as if to critique some sort of free-market system based on individuals, and I wanted to emphasize that the system we have can solve those problems.