I think 公價人情 for each person is $500 (minimum)
一家三口去飲: $500 x 3 = $1500
But I will not bring my kid as I don't want to pay extra $500 as my kid will not eat much!! I am just willing to pay $1000!!
Normally I will just tell my friend that I will not be available as I need to take care of my kid at home, so I will just give $300 for no show (and ask her / him not to give me the red bomb)!