This is something I realized working on one of our global brands about a year or so ago. After creating around 20 unique pages at 2x and looking at all the file sizes for three device sizes and thinking it was just insane how large they were. I just couldn’t understand why we were doing it, every time I tried to preview designs in browser it gave me issues, but it was the math that pushed me over the edge. The point I realized we were doubling everything and the Devs were halving it I decided we had to change it.
It was actually very easy to convince the other designers (some which were much more senior than me) to join me using basically the same talking points to convince them. We since started building psds at 1x with all images sized to 2x then converted to smart objects at 50% and it helped us cut our file sizes to less than half.
This was a great read and I hope more designers start thinking this way. I hate when I inherit a file structure at 2x because it adds so much unnecessary effort.