Economy

The  of the Commonwealth actually feels more like a real thing now. Caps are much more valuable than they were in vanilla Fallout 4. Many items and services (such as doctors) are more expensive, and you will often find yourself actually needing to use them occasionally now. You may even need to buy cooked Food (Cooking Station) and Water (Purified Water), something that probably was rarely ever done before.

Ammunition (Ammo) is very expensive, and more difficult to find. You will most likely find yourself buying ammo wherever and whenever you can. You may want to consider a wider range of weaponry to make use of different ammo. Ammo crafting is now available in Horizon too.

Bartering is more normalized, because of the fact that items have such high prices now. What this means is the maximum range on prices won't be as drastic as it used to (mainly due to the lack of charisma.) I'm not completely satisfied with the state of bartering, but it's much more balanced than vanilla FO4.

General Changes

 * Ammo and medical supplies are significantly more expensive
 * The maximum value you can sell items for is lowered to half the value of the item (down from 80%)
 * Buy prices can also be reduced to an even 100% of their listed value
 * Vendors take 7 days to restock their goods (5 days with my Timescale Addon)
 * Each vendor is overhauled to be more unique, and provide specific goods
 * Vendors stock less rare goods than usual
 * Purchasing Home Plate is reduced to 950 caps, and it works with the new fast travel system (Caravan Travel)

Weapon Vendor Changes

 * Vendors now sell raw ingredients for crafting ammunition, explosives, and fusion cores
 * Weapon vendors will now sell loose weapon mods and a bigger variety of them (most vendors didn't even sell any before)
 * Loose weapon mods sold on vendors will no longer roll "standard" (since it's a waste of a roll)
 * Weapons sold on vendors are no longer modded, and sold in "packages"
 * All "standard" mods are valued at 1 now, so they can't be re-sold for anything
 * All loose mod values are rebalanced
 * Vendors never sell Fusion Cores, but they sell parts for them now
 * Fusion Core value has been greatly reduced (below vanilla value even.. because of the way their health works)
 * The prices on unique weapons and armor is rebalanced (some are more expensive, some are less)
 * The personal weapons/ammo that vendor NPCs have should no longer appear in their stock (for most NPCs, not all)
 * Certain ammo types are unrealistic to be on most vendors: (you'll need to craft or loot them now)
 * Cryo Rounds, Cannonballs, Alien Blaster Rounds will no longer appear on vendors
 * Railway Spikes, Gamma Rounds, Flamer Fuel will only appear on appropriate vendors
 * Doctor vendors: No longer sell chems
 * General Stores: Has a chance to sell only basic low level ammo types
 * DLC: Because of the odd respawn times for DLC vendors, most DLC vendors have significantly less goods for sale
 * DLC: Weapon vendors can sell DLC ammo packs, but only have a chance to spawn them
 * DLC: Harpoons will only appear on some DLC vendors (this ammo type is expected to be crafted if you want to use it often)
 * DLC: Some Commonwealth weapon vendors have a chance to sell DLC ammo above level 8

Ammo Packs

 * Ammo is now sold on vendors in "Ammo Packs", which contain preset amounts of ammo that vary based on type
 * Values for Ammo Packs are based on average damage output of the round
 * Loose ammo is generally not supposed to be sold on vendors anymore
 * Ammo packs allow the game to be better balanced around ammo buy/sell pricing

Other Vendor Changes

 * Crops on all vendors are now only sold in "Bundles" (the amount varies based on the type)
 * All individual crops are lowered in value

Diamond City - Weapons

 * Sells a standard variety of ammo and ammo-based crafting mats
 * Sells a moderate variety of weapons and loose weapon mods

Goodneighbor - Weapons

 * Sells pre-war military themed weapons, explosives, and explosive crafting mats
 * Sells loose mods based around certain pre-war and heavy weapons

Cricket

 * Sells "raider" style weapons/ammo/mods, and some melee weapons
 * Sells some weapon/explosive materials, and some chems

Carla
Sells mostly junk only, but a lot more of it

Rufus
Sells mostly tools and parts only

General Stores

 * Sells mainly misc junk and some assorted food/chem/medical items
 * Sells less ammo/weapons/armor now

Brotherhood - Weapons

 * Sells energy weapons, energy ammo, and energy crafting materials
 * Sells 5mm ammo, missiles, and heavy weapons
 * Sells loose mods based on energy and heavy weapons
 * Sells Fusing Casings, used to craft Fusion Cores
 * Sells some ballistic ammo
 * Sells 10-pack of Vertibird Signal Flares
 * Sells T60 Power Armor pieces (same as before)

Railroad

 * Sells a select variety of weapons, ammo, and mods
 * Sells an Ammo Pack of Railway Spikes
 * Sells 10-pack of Standard Flares
 * Sells the usual other RR stuff

Workshop Weapon Vendors

 * Tier 1/2: sells basic ammo and weapons
 * Tier 3/4: sells additional ammo, weapons, crafting materials, and explosives

Farms

 * Vendors at most farms now actually sell crops and farm-related items
 * Abernathy Farm, The Slog, Finch Farm, Graygarden, Warwick