And manufacturers do a sneaky swap too, my Coway 150 which is a great air filter by the way, came with a nice thick grid of hexagonal cells each filled with carbon granules - that insert alone weighs like half a kg. I ordered official filter and carbon filter replacements off their website ....got a thin carbon "foam" that weighs maybe 50g instead.
If anyone wants to get serious about VOC filtering, these things have 7 pounds of carbon in them, they’re made for filtering the air of weed grow ops: https://terra-bloom.com/collections/carbon-filters
The real activated carbon filters have 10s of pounds of carbon. The little black foam thing that comes with those 2-in-1 carbon filters is useless.