There are many factors that contribute to the price of an artwork, materials, time involved for completion, complexity etc.
Generally a watercolour portrait on paper would take several hours and would cost around AU$150, while an oil painting on canvas would usually start at around AU$300 due to the time required as it's a slow medium to work with. A charcoal sketch on paper could be done for around AU$50-100.
Having said all that, every job is different, so contact me below with a general idea of what you are after and a general budget and I can set you up with a quote.
Thanks for your interest in my art.