These Halloween stores are seasonal popup retailers operating under a franchise program. A few who operate multiple franchises actually put the time and effort into selecting stock. However most of the time....
The franchise owner simply pays a flat fee for a store package. This package is a fixed retail stock package along with rudimentary branding material like store banners. If 10 stores ordered a $25,000 store package, all 10 stores would open with an identical stock of merchandise. Most chains offer store packages on multiple price levels, plus packages to equip the store with registers and shelving. They also force the end of season discount sale, because old merchandise is discontinued in the register system during the off season.
The side effect of this is that franchise owners who go with this package system have to stay in the package system for the season. The only way they can possibly restock is to buy another package. Not all merchandise is included in all packages. That means if a franchise owner started with a $250,000 package, he would have to order another $250,000 package to ensure he was able to restock anything he opened with, and doing that is quite often not cost effective for the store owner.
The package system is preferred by the Halloween chains because most of their merchandise is produced by part time manufacturers who will retool their factories to produce Halloween goods for a certain period of time before moving on to the next contract job. This manufacturing happens well in advance of the sales season. Forcing the package system means they can place orders for fixed quantities without needing to worry much about shortages or restocks.
Probably 90% of the Spirit stores are operated under this system. Of the 10% who customize their ordering, most of them allow Spirit to handle inventory tracking and restocking remotely, rather than doing it themselves. Even in that situation, restocking cannibalizes web sales inventory, rather than coming from a dedicated restock inventory.