Hello! I would need to know the details of the project, first. The subject matter of the illustration, is it a publication (if so, what kind of, is it a cover image or other, and how many copies will be printed, and who is the publisher). The deadline schedule affects the price as well, so urgent commissions (from a couple days to a couple weeks) are more expensive than less urgent ones (a month or more). I typically calculate a price depending on how many work hours I will estimate the illustration to take, and the actual charge per hour depends on all the other details mentioned above. This painting took me about 22 hours of work (included the time taken for subject research).
If you are interested in commissioning me, please send me more details about your project via email: ulla (dot) thynell (at) gmail (dot) com and I'll be able to answer more precisely. Thank you!