This mod was created to go alongside mods that change shop inventories--most (or at least from what I've seen) don't change the buying values of items, so you can buy rarer items for pretty cheap. This makes them more expensive, or all items more expensive. Also added optional non-supply knives and carry more traps versions, as this mod will overwrite mods that affect those as they edit the same file. Please note this mod does not affect the shop itself and what items are buyable.

Here's the price changes for some of the rarer, usually non-buyable items (should be the only price changes found in the Rarer items Only versions of the mod): 
Nulberry: 1200
Dash Juice: 2000
Mega Dash Juice: 4000
Might Seed: 500
Demondrug:2000
Mega Demondrug: 5000
Might Pill: 3000
Adamant Seed: 500
Armorskin: 2000
Mega Armorskin: 5000
Adamant Pill: 3000
Whetfish Fin: 3000
Whetfish Fin+: 10000
Sushifish Scale: 500
Great Sushifish Scale: 2000

Explanations of the different versions (note: choose only one file, they will overwrite each other):
Increased Item Prices-Most Items:
Increases all of the prices of items to be more expensive, with the exceptions of special items (mantles, whetstone, etc), mining materials, and monster materials. 

Increased Item Prices-Most Items Carry More Traps:
Increases all of the prices of items to be more expensive, with the exceptions of special items (mantles, whetstone, etc), mining materials, and monster materials. You can carry three trap tools, pitfall traps, shock traps, and EZ variant traps as well. 

Increased Item Prices-Most Items Knives Non-Supply:
Increases all of the prices of items to be more expensive, with the exceptions of special items (mantles, whetstone, etc), mining materials, and monster materials. Throwing Knives are no longer supply items and can be kept after quests/expeditions. 

Increased Item Prices-Most Items Knives and Traps:
Increases all of the prices of items to be more expensive, with the exceptions of special items (mantles, whetstone, etc), mining materials, and monster materials. Throwing Knives are no longer supply items and can be kept after a quest/expedition. You can carry three trap tools, pitfall traps, shock traps, and EZ variant traps as well

Increased Item Prices-Rarer Items Only:
Increases the prices of rarer items to be more expensive (see list above). 

Increased Item Prices-Rarer Items Only Carry More Traps:
Increases the prices of rarer items to be more expensive (see list above). You can carry three trap tools, pitfall traps, shock traps, and EZ variant traps as well. 

Increased Item Prices-Rarer Items Only Knives Non-Supply:
Increases the prices of rarer items to be more expensive (see list above). Throwing Knives are no longer supply items and can be kept after quests/expeditions. 

Increased Item Prices-Rarer Items Only Knives and Traps:
Increases the prices of rarer items to be more expensive (see list above). Throwing Knives are no longer supply items and can be kept after quests/expeditions. You can carry three trap tools, pitfall traps, shock traps, and EZ variant traps as well. 

Choose only one file. 

Compatibility: Incompatible with mods that change the selling or buying price, supply status, or carry amount of items--or mods that change the  itemData.itm file. Compatible with mods that add or remove items from shops or other places. 

Permissions: Don't sell it or put it behind a paywall. Otherwise, do with this mod as you wish.