That was the savings estimates at the time from sources in the government iirc so I think they would have included the relative durability of the cotton bank note in the calculations. [0] Of course that's just the savings not the costs but a lot of those are one time as different coin op mechanisms get updated to accept dollar coins.
[0] The $1 notes also go through a lot more use in their life so they degrade much quicker iirc and a bit over 40% of the bills in circulation are $1 bills too so switching over to a coin that lasts decades instead of 6-7 years (https://www.federalreserve.gov/faqs/how-long-is-the-life-spa...) would really cut down on printing costs.
Printing is just not very expensive, relative to the size of the US economy. People like the $1 note. I just don't think it's going to happen for another 2x-4x reduction in the value of the note.
Give it 15-40 years and we'll think about it again!
Of course, by then, so much of commerce will be electronic that I don't think anyone will care about what notes still circulate, other than the $100, which is used more outside the US than inside.
It's not _just_ printing though it's transport, storage and distribution then at the end of it's life span collection and destruction. In 2023 the US printed 2,397,104,000 in $1 bills alone. Doing anything at that scale is not cheap no matter how inexpensive a single unit of production is.
[0] The $1 notes also go through a lot more use in their life so they degrade much quicker iirc and a bit over 40% of the bills in circulation are $1 bills too so switching over to a coin that lasts decades instead of 6-7 years (https://www.federalreserve.gov/faqs/how-long-is-the-life-spa...) would really cut down on printing costs.