It honestly depends on the artist.
The commission artist I usually go to (@/ZamiraArts) has very reasonable prices, for example,
Semi Realistic: Head $15, Part Body $25, Full Body $30 (per character I think)
But then there are other artists who charge a little less or a little more than that. If it helps, you could just find commission artists through Instagram by looking at people’s tagged to see the tagged artist.