Tank level inaccuracy causing long wait times before print

An idea I had proposed in the past was for us to be able to weight the resin cartridge, then enter that value in preform before each print.
Preform would have a database with all cartridges (empty and full weight), and that would give a much closer estimate.

They have implement a weight sensor in the 3L, but not on 3/3+. A cheap way of thinking in my opinion, what would be the cost of it??