Shop

Not to be confused with The Shop, a floor in Greed mode.

A shop is a room that sells various items in exchange for pennies. Shops require a key to open (unless Isaac holds Store Key) and appear in chapters 1, 2, and 3 (and 4 if Isaac holds Silver Dollar). One also appears in ???. Only one shop will spawn in these floors, even when under the effect of Curse of the Labyrinth.

In Greed mode, Shops are twice as wide as usual and do not require a key to enter. It always contains a key, a red heart, an item from the Greed mode shop pool, an item from the Greed mode boss pool, and two random pickups, trinkets, or items from the Greed mode treasure room pool. A new item will spawn after an item is purchased, as if Isaac is under the effect of Restock.

Merchandise

Shops can sell red hearts for 3 pennies. They can also sell soul hearts, bombs, keys, batteries, Pills, and tarot cards for 5 pennies each.
After reaching Lv. 1, the shop will start selling pedestal items for 15 pennies. A list of items that can be available for sale can be found here.
Randomly, the prices will be halved and in red. Hearts will be 2 pennies, other pickups will be 3 pennies, and the pedestal items will be 7 pennies. Steam Sale will make this happen 100% of the time.
There is a 20% chance for donation machine to be replaced by restock box. ^{[Check ingame]}

Levels

Shops start at level 0, and can be upgraded through the donation machine, which can be found in the shops and sometimes in arcades, vaults, black markets, and rare room layouts. Each level increase adds to the shop's background and affects how many items are available.

Level	Coins donated	Shop stock
0	0	2 consumables available for sale
1	20	2 consumables and 1 pedestal item available for sale
2	100	3 consumables and 1 pedestal item available for sale
3	200	3-4 consumables and 1-2 pedestal items available for sale (always 5 total items)
4	600	4-5 consumables and 1-2 pedestal items available for sale (always 6 total items)

Rare variants

There is a small chance for the shop to be replaced by one of its two rare variants.

The two pennies are lucky pennies. This variant will not appear unless the level 4 shop upgrade has been unlocked.
This variant has a small chance to appear in any level of store upgrades.

Notes

Using a Credit Card in the shop will make everything for sale free, spawning item pedestals and removing all list prices. However, Restock only replenishes items that are bought for a listed price.
Having Store Credit will cause all items to be available for $0, but will be consumed upon making a purchase.
If the Store Credit effect is gained through Error, it will not be consumed; this can be combined with Restock to break the game.
Using Rune of Jera creates a free copy of all pickups, even if they haven't been purchased.
- Diplopia will do the same thing, but with pedestal items as well.
Usually, you must use a key to open the shop, but IX - The Hermit, "Curse of the Maze", Dad's Key, bombing through the secret room, and Store Key can allow you to enter without using a key.
The shop's door is identical to the Library, and if you have no items that make it otherwise, their symbols in the minimap will also be the same. The shop can never spawn next to the starting room of the floor (except for Basement I/Cellar I), so it is a good way to tell if it is a library or not.
Shops also have a chance of being replaced by a miniboss room containing Greed or Super Greed. Rib of Greed will remove this risk.
Acquiring two Steam Sale will result in all items in the shop being free. This can be combined with Restock to enable infinite purchases. Further combining this with Chaos will allow the player to exhaust a lot of item pools until Breakfast is the only thing that appears back in the shop.
Restock will cause stores to spawn new items after purchase.
If II - The High Priestess is used in a room with a dead shopkeeper, the foot will target it and stomp on it.
There is a small chance when you bomb the Shopkeeper that they can turn into Greed and start attacking you.
If enough items are purchased to empty the shop pool (without picking up Chaos), shop items will begin to draw from the treasure room pool. When that pool is exhausted, only Breakfast will spawn.