The spigot rules page for premium plugins has been updated one week ago. Some nice changes:
Pricing
https://www.spigotmc.org/threads/premium-resource-guidelines.31667/
Pricing
- It is up to you to pick appropriate resource pricing for your resource.
- Resources with higher prices will be scrutinized more than those with lower prices.
- The following limits apply (USD or foreign currency equivalent)
- Minimum Price: $0.99
- Maximum Price: $19.99
https://www.spigotmc.org/threads/premium-resource-guidelines.31667/