I already own the hardware, so I only pay for colocation and transit. It's probably a lot less than you think. I hope to find some way to monetize it, but it is cheap enough that I can keep it running for quite a long time without any income.
Not exactly. Attachments are only fetched from Discord as the user requests them. This means that the vast majority of attachments are never stored on my server. Right now, I only have about 280TB of attachments locally on my own infrastructure. You can see more stats here: https://searchcord.io/about
Thanks for your question!