The new difficulty options menu from Ver. 1.11.36 covers many bases already. Still, certain tweakworthy aspects of the gameplay remain untouched - the Sell Price (ie how many credits you earn when selling items to vendors) is one of these. 

By changing the sell price you control how the ingame economy works out for your character. While lower sell prices generally make it harder to get rich, they also shift gameplay priorities:  High sell prices make looting items and outpost mass production very attractive, while low sell prices emphasize mission rewards and cred sticks found as these become relatively more valuable compared to looting and producing. Generally, low sell prices tend to free you from the urge to pick up everything.

DOE Sell Price has five settings:

Very easy - 400% of the vanilla sell price | suggested - 4% XP Modifier 
Easy - 200% of the vanilla sell price  | suggested - 2% XP Modifier 
Hard - 50% of the vanilla sell price  | suggested +1% XP Modifier 
Very hard - 25% of the vanilla sell price  | suggested +2% XP Modifier
Extreme - 10% of the vanilla sell price | suggested +4% XP Modifier

05/18/2024: Based on request I have provided an additonal file that sets the Sell Price to 70%.
05/20/2024: Added alternative .esm version of the mod (need Plugins.Text Enabler then)
05/21/2024: XP Modifiers can now be realized via XP Unchained

How it was done
DOE Sell Price is realized via the Console Command Runner Updated mod, which runs the respective included .toml file for one of the five settings of DOE Sell Price.

Installation

• Please install Console Command Runner Updated at Starfield Nexus - Mods and Community (nexusmods.com) (which requires SFSE and the SFSE Address Library Plugin)
• Download the DOE Sell Price mod, unzip it and place the .toml file of your chosing into the folder ".../Data/SFSE/plugins/ConsoleCommandRunner"
  

Credits
Hugs to Bobbyclue and Meridiano for  Console Command Runner Updated at Starfield Nexus - Mods and Community (nexusmods.com)
Finally, without xEdit and Elminster's work of a genius all this would not be possible, so, many kudos to Elminster and team.

The whole DOE Series and friends
DOE Resources
DOE Resources at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Sell Price
DOE Sell Price at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Starpower
DOE Starpower at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Loot
DOE Loot at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Ammo Rarity
DOE Ammo Rarity at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Ammo Prices
DOE Ammo Prices at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Skill Progression
DOE Skill Progression at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Research
DOE Research at Starfield Nexus - Mods and Community (nexusmods.com)
DOE Less Shortcuts
DOE Less Shortcuts at Starfield Nexus - Mods and Community (nexusmods.com)
Replicant
Replicant at Starfield Nexus - Mods and Community (nexusmods.com)
XP Unchained
XP Unchained at Starfield Nexus - Mods and Community (nexusmods.com)
Sneak Damage Hotfix
Sneak Damage Hotfix at Starfield Nexus - Mods and Community (nexusmods.com)
Equipment Level Requirements (ELR)
Equipment Level Requirements (ELR) at Starfield Nexus - Mods and Community (nexusmods.com)
NGXP Plus / NGXP Plus Risk
NGXP Plus at Starfield Nexus - Mods and Community (nexusmods.com)
Minimum Enemy Level
Minimum Enemy Level at Starfield Nexus - Mods and Community (nexusmods.com)
Fauna Protection Initiative
Fauna Protection Initiative at Starfield Nexus - Mods and Community (nexusmods.com)
Spongecop
Spongecop at Starfield Nexus - Mods and Community (nexusmods.com)
Building Rarity
Building Rarity at Starfield Nexus - Mods and Community (nexusmods.com)
Minimum System Level
Minimum System Level at Starfield Nexus - Mods and Community (nexusmods.com)