Under storyteller difficulty in custom playstyle settings, adjusting the slider 'Turret Rearm Cost' has no effect on the rearm cost of turrets. This is case at the start of the game (initial difficulty selection) and when adjusting during an active game.
Recreate:
1. Start a new or load a current game (use god mode for new game)
2. Go to an existing turret or build one.
3. Select the turret, view information (the little 'i' in the bottom left corner).
4. Check the 'Building', 'Rearm Cost' (Make note of it)
5. Go to the menu, options, storyteller settings
6. Select Custom
7. Adjust the 'Turret Rearm Cost' Slider to any figure (go 1% so it would be obvious).
8. Select any turret on the map, view information (the little 'i' in the bottom left corner).
9. Check the 'Building', 'Rearm Cost'
10. Note, it has not changed (rearming the turret will also show that you will use that cost, not what it should now be).
Rimworld Core, Royalty and Ideology (No Mods).
Hoping others can confirm they have the same issue, otherwise I'll try a clean install of Rimworld and see if the issue is only on my end. I first noticed it with mods and modded turrets interestingly did adjust to this slider, only vanilla turrets were uneffected (I confirmed it in vanilla too, with not a single mod active but I want to rule out this been a one-off).
Can confirm for mini-turrets without mods on a clean start. Will always try to put in 80 steel at 0 fuel, even with rearm cost is set to 1%.
Thanks for the bug report. I appreciate the detailed reproduction steps, made it very easy to reproduce. I have confirmed this bug in 1.3.3242 and will get a report into the devs.