Recipes that have 2 ingredients, and a price multiplier, dont aply the multiplier to the buyB ingredient.

For example, summon the following villager with a trade of 30 emeralds and 30 books for an item with a gossip major positive of value 100 (so it can be seen clearer), 

Apreciate on the screenshot, how emeralds went from 30, to 4, and how the books stayed at 30
even though, there is a discount aplayed.

A consecuence of this, is that Librarians (among other professions) from before 1.14 (Village and Pillage) bought a book (buyA) and emeralds (buyB), since they only buy one book, in the newest version, there is no discount aplied whatsoever. 

Command for summoning the villager on the screenshot, whough, you have to insert your UUID for it to work on you

/summon minecraft:villager -456.63 30.00 207.58 {Brain: {memories: {}}, HurtByTimestamp: 0, Attributes: [\{Base: 0.5d, Name: "minecraft:generic.movement_speed"}], FoodLevel: 0b, Invulnerable: 0b, FallFlying: 0b, ForcedAge: 0, Gossips: [{Target: [I; 1509418199, -1014021782, -1308436573, 410644764], Type: "minor_negative", Value: 135}, {Target: [I; 1237034724, 594364694, -1598532237, 898294054], Type: "major_positive", Value: 100}], PortalCooldown: 0, AbsorptionAmount: 0.0f, LastRestock: 0L, FallDistance: 0.0f, DeathTime: 0s, Xp: 0, LastGossipDecay: 10560717L, HandDropChances: [0.085f, 0.085f], PersistenceRequired: 0b, Age: 0, Motion: [0.0d, -0.0784000015258789d, 0.0d], Health: 20.0f, LeftHanded: 0b, Air: 300s, OnGround: 1b, Offers: {Recipes: [{maxUses: 10, buyB:

, buy: {id: "minecraft:emerald", Count: 30b}, sell: {id: "minecraft:blackstone", Count: 10b}, xp: 1, uses: 0, priceMultiplier: 0.05f, specialPrice: 0, demand: 0, rewardExp: 1b}]}, Rotation: [52.058212f, 0.0f], HandItems: [{}, {}], RestocksToday: 0, ArmorDropChances: [0.085f, 0.085f, 0.085f, 0.085f], Fire: -1s, ArmorItems: [{}, {}, {}, {}], CanPickUpLoot: 1b, VillagerData: {profession: "minecraft:librarian", level: 2, type: "minecraft:plains"}, HurtTime: 0s, Inventory: []}