I admit my mistake, I just quickly looked up the cheapest HDDs on google and saw some for 40 USD but it looks like they aren’t for sale anymore or something. Still, a WD Red goes for 70 bucks, which is half the price of a SSD of that size while also being more than good enough for movies.
I got excited about a sale on toilet paper. It was 50% off for 30 rolls of the really high quality one!