Reddit only started hosting images and videos a couple years ago. That alone would massively add to costs. It’s self inflicted and seems it was planned in an effort to keep people on the platform instead of linking to imgur to view the picture.

They brought the added overhead on themselves

well, they hired thousands of devs in the last few years, only to direct their efforts to self-hosting videos, chat features, customizable snoo avatars you can sell NFTs for, etc. (you know, things people wanted)

so I can understand the loss potentially growing in recent years, given what they’ve been spending on