Photography - not much unless I buy used, which is what I usually do. So some funky old lenses and adapters to get on the body, which usually nets some fun results.
Data hoarding - a couple of hard drives. Which I should really do, I'm coming close to 5% free (which sounds like less than it is when you've got about 115tb, which is why I'm not rushing out).
Computer Vision / AI - more processing power! But I make work buy me that stuff so its fine.
General compute - about 5 more tiny/mini/micros at the usual price (plus the usual upgrades) to either ads to the cluster or make a new one! Or one or two of the newer little beasts that I will probably be waiting another year or two to pick up.
Bicycling - a good bike for getting around! My bike is about 15 years old now, it was new old stock because no one liked the color apparently - which made it about 1/2 the price of what it should have been. I've been replacing gear on it over the years, but I'm tempted to buy something new, honestly less for going fast and maybe more upright, like a hybrid. Which I can get an OK model at that price.
I kid of course, I could use a hobby that incorporates some kind of motion.
But for real $1k is part of a good used lens, a fifth of the camera I really want, or a couple of decent hard drives to add to the collection. I remember I once lost my shit over $10, now I can't even get it up for $1000.
Thats just my main NAS + a media NAS. I also have a backup NAS that replicates the main (well, a lot of it, just the things I'm concerned about backups for) which also is a remote backup for family (where they also have a NAS I set up that is their local storage + my compressed backups).
Which is why my dumb ass is thinking of replacing the two 14ru racks I have with a 44ru (and space for a second) where I hope to be moving within the next year or so.
Sometimes, things don't always stay around on the internet, so if there's something I'll want to watch or listen to again, I keep it local. Or if there is something that should be preserved, like the data dump of patriotfront that is continually seeding.
It relates to my hobbies, too - all of my photos are stored in raw plus my edits. I am also converting all of the VHS tapes my dad recorded of the family over the years and I serve them up to my family on my media server, along with the videos of different things of my kids, like dance recitals.
More recently we've seen the intentional removal of information on the internet specifically with the US government, so where possible I've backed some of that up as well and contributed it to appropriate groups.
Then of course there's music, movies, tv shows, documentaries, books, comics, and so on, even fan created edits of shows and movies like despecialized edition and 4k77, Harry Potter and the deathly weapons, hackers the 56k upgrade, etc.
Its not meant to just hide on a drive, so its all served up with various services I run, such as jellyfin, audiobookshelf, kavita, etc.