SRAM makes some comparisons about the increased range of their 12 speed crank and cassette combinations, compared to 11 speed in this cycling tips article, but fails to make a legitimate comparison of what can be done with traditional chainring combinations and an 11T smallest cog, like Campy has already done, using the same hubs that work with 9/10/11 speed. Sprinters have used a 54 or 55T big ring for many years, to get the same 5:1 gear ratio as the 50/10. Campy has all of the 1 tooth shifts on their 12 speed cassettes, that make any sense (11-17). The 18-19 shift is rarely considered to be of any value because the percentage difference is only 5%. The 11-12 shift is 8.3%. while a 10-11 shift is 9%. You can't get something for nothing.
https://cyclingtips.com/2019/02/sram...ap-axs-review/
There is no magic to getting range. If you want more range, you either have to increase the percentage difference between the rings or make some bigger jumps between some of the larger cogs.
I could upgrade from Campy 11 to 12, with only shifters, cassette, FD and RD, for less than $1000, but all I'd gain is an 11T cog that I don't need. I use a 12-32, because I can get all the speed I need on the flats and I let gravity take me up to 50 mph on the steep descents. I have 1T shifts, all the way to the 17T, just like Campy 12 speed. Campy will probably offer a Chorus 12 group in 2020, to make 12 speed more affordable.
I'd be interested to know how close Campy 12 and SRAM 12 cog spacing is.