What's the formula to calculate townbell daily upkeep?

[porcobuddha]

Is it the same formula used for the pclaim?

[Procne]

Not really. Drain is proportional to the max authority. Drain = 6.666% of max authority
Town bell drains 40 authority per day (can someone verify?).
Cross of saint george increases the drain by 5 (75 authority = 5 drain).
Boundry stone increases the drain by 3 (45 authority = 3 drain).

[Feone]

Town bell is slightly higher in upkeep/tile than pclaim iirc. However, claiming a pclaim the size of an equivalent town claim would take so much silver it offsets the costs easily.
You'd have to maintain the pclaim for many months, if not year(s) before the difference in silver pay itself back. Not to mention the reduced security compared to a townclaim.