I worked on NIP13 for text notes in nostr_rust and got the below

Avg for difficulty 5 is 0 milliseconds

Avg for difficulty 10 is 3.5 milliseconds

Avg for difficulty 15 is 70.8 milliseconds

Avg for difficulty 20 is 2891.2 milliseconds

Avg for difficulty 25 is 44998.4 milliseconds