I charge $200 per hour of tattoo time. My minimum is $600. Tattoo sessions can be expected to take anywhere from 3-5 hours, with most averaging at 4 - you can expect to pay $600 to $1200 a session.
Below are some examples:
Single session, 3.5 hours, $700.
Single session, 4 hours, $800.
Two sessions, 7 hours, $1400.
3 sessions, 12 hours, $2400.
4 sessions, 16 hours, $3200.