We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
Online, you aren't getting 6TB+ for under $100 without going used or very sketchy. The best I see at a reputable vendor like B&H Photo is a new 6TB external WD for a Black Friday sale price of $130. Just look at https://shucks.top/, what you want isn't happening.
Watch your local Costco, Best Buy, Walmart stores - you might get lucky if they put out a palette of externals for a special price.