Tattoo artists are like hairdressers and waitresses...tip them! Especially when they go above and beyond the call of duty and truly make your piece better than what you are paying for it. Did a $700 piece on some kid yesterday. Was supposed to take around 7 hours, ended up taking me almost 12. When i was done with it, i had used almost twice as much ink as I had originally planned. He says "wow, you really did more than you said you were going to, it looks way better than i could have ever imagined." "How much?" "Technically...upwards of $1000, but hey...i quoted you $700 last week...so $700 it is" "Sweet, and heres a tip..." *gives me $715.* I would expect a good tip to be for every $100...throw them an extra $20. If he really goes above and beyond... i would expect a good tip to be...$50 every hour...to accomidate for ink costs and lost time.