It's a very large markup on the small-user retail cost of the basic thing they're providing (web-accessible, access-controlled file storage—see, for example, BackBlaze B2) but that's utterly typical of services that can get away with charging you a "convenience fee" for that sort of thing once you're on their SaaS. 2-3x markup isn't unusual, and that's about what this is, and that's above typical retail—even if GH's not managing the storage and such themselves, they're likely getting an even better (bulk) rate.
