It's not:

In July 2024, running a Relay on ATProto already required 1 terabyte of storage. But more alarmingly, just a four months later in November 2024, running a relay now requires approximately 5 terabytes of storage. That is a nearly 5x increase in just four months, and my guess is that by next month, we'll see that doubled to at least ten terabytes due to the massive switchover to Bluesky which has happened post-election. As Bluesky grows in popularity, so does the rate of growth of the expected resources to host a meaningfully participating node.

https://dustycloud.org/blog/how-decentralized-is-bluesky/