"In 2024, it cost $N to run a Mastodon instance with ~1000 active users for a year. By the end of 2025, that figure had dropped to $0.5X, due to the launch of X, Y, Z."
What are X, Y, and Z?
In terms of cost, consider systems administration and moderation as paid work, even if the admin is not paying themselves for either of these things.