right now the biggest cost is llm api calls (currently claude haiku) for organising content and making it easily searchable - this is relatively cheap (max 50$ per month). I use pinecone for search which so far has been very inexpensive, though admittedly traffic has been low, so I'll see how that goes.

on feeds - I've built a list over a number of years, a mix of tracking blogs on twitter, hacker news and a few other places. usually the feed url can be lifted quite easily from a blog's header.