This is from January 30th. Since then Bluesky has opened up to everyone (no invitation required), allows you to host your own PDS and even added new community based moderation tools known as Ozone internally, but acts a a "labeling service". It allows those who subscribe to them to get more specific tailored content they don't (or in some cases do!) want to see and it is labeled with a tag on accounts or posts, then the end user can choose whether they want those posts to have a warning on them, be completely hidden or nothing at all. It allows much more customized options & Bluesky doesn't need to actively close or ban accounts that might just include content other people don't want to see.

From the stats of people who ran their own PDS for their own accounts, it used an less than 1mb of data transfer a day and insignificant amounts of CPU/RAM (less than a 20% spike). But, it will depend on how big your account is, how many followers you have, number of posts you make, etc etc.

In native Bluesky with a default account, they have decentralized the servers so there are maybe around 20-30 servers all on the East Coast of the US. There's currently not much incentive to run your own. The PDS software is fairly new and unless you just wanted to have a non-US host for privacy reasons, you could do so and get away with running it on a RPi or standard VPS no problem. No one has yet started any major instances to rival the primary ones yet, however.