Update - September 24: In a new blog post, Microsoft confirmed that Xbox Series X storage expansion cards will cost $220. They will be released worldwide alongside the Series X and Series S on November 10.
Director of program management Jason Ronald explained the price point in the post:
"This level of consistent, sustained performance requires advanced components which come at a higher cost than traditional hard drives or SSDs often found in PCs. By partnering with an industry leader in Seagate, we worked together to deliver an expandable storage solution which delivers identical performance at the lowest cost possible and available this holiday."
Best Buy has listed a Seagate's 1TB Xbox Series X expandable hard drive for $219, giving us a good idea of how much it will cost to increase the storage capacity of Microsoft's next-gen console.
The device also says it will be compatible with the Xbox Series S, which is scheduled to launch alongside its beefier next-gen sibling this November 10 worldwide.
It's unclear how much Seagate's hard drive will cost in the UK, or what prices to expect from other similarly sized hard drives from third-party brands, but you can already pre-order this one so that it arrives the day after the Xbox Series X/S release.
The Xbox Series X already ships with 1TB of SSD storage, but the Xbox Series S is a lot smaller, with just 512GB included as part of its much lower price point.
We're not sure how big exactly games are going to get on the next-generation of hardware, but the likelihood is that if you're someone who plays a lot of games, and doesn't want to delete old favourites for new releases, an external hard drive will be a must buy.
Here's everything we know about Xbox Series X pre-orders too, or watch the video below for a look at the next generation of Unreal Engine.