Retail store Best Buy recently revealed the prices for the upgrade storage on Xbox Series S/X.
After the reveal of the next-gen Xbox console systems, it was apparent that consumers could expand the storage with an expansion. No information was given about the prices on that day other than Microsoft partnering with Seagate to create proprietary expansions cards about the size of a flash drive. According to the source, these were Gen 4.0 PCIe SSDs that have the same speeds as the internal storage drives.
The online portal for Best Buy recently revealed the prices of these expansion cards and they are expensive. According to the dedicated page for the items, they are priced for $220. That is almost half the price of the Xbox Series S. Only Best Buy has them for pre-order right now.
So if you plan to expand your storage space for your gaming library, you might want to save up more for the expansion cards.