This is a modder resource, this does not modify any prices on its own.
Using .json config files you can adjust buy / sell prices of any item (based on keywords), and restraint that to specific conditions.

Since 1.0.2 in Barter menu you'll be able to see which items are cheaper or more expensive than usual, they are highlighted with an indicator, this is compatible with all UI mods, and can be customized or completely turned off via the config json file.

An example config file is provided to showcase what the mod can do, which does the following:

Better priced potions & poisons when you yourself are an alchemist
10% senior discount for purchases! (at least 1000 days have passed in game)
Due to the civil war and shortage of supplies for soldiers, in Windhelm weapons and armor can be sold for more money and also cost more to buy.
More favorable prices from all Orc tribes, after completing The Cursed Tribe quest.
On Middas days you get better prices from vendors of the opposite sex.

Compatibility
All mods are compatible, this does not modify any forms, or any files in vanilla.
Tested only with Skyrim 1.6.1170 but should be compatible with all versions.
Safe to install or uninstall at any time.

Source Code
Project source is available at Github.

Credits

SKSE development team
Mrowrpurr for their tutorials
Ryan (SniffleMan) for CommonLibSSE
powerof3 for their fork of CommonLibSSE
charmedBaryon for their NG fork of CommonLib

Dynamic Pricing Framework

Gallery

Main file

Dynamic Pricing Framework

Optional files

Example config file

Debug ESP