Do you charge by hour or by piece?

I think it depends on a piece, once you get an appointment the artist will be able to give you an estimate of the cost. I personally recommend CJ Esparrago, he did a wonderful job with tattoos for me and my fiance.

$120 an hour

How much per hour or it depends on the piece?

My wife got a piece done. It was hourly, though they're pretty good at estimating the time required.

I Got A Piece Done There & It Was By Hour