I’m a realism artist myself and I have commissioned another one in the past because I prefer to have others do it so I can focus on writing but the realism price range is $300+ AUD per piece. Other artists tend to charge anywhere between $80—$200+ USD for semi-realism or anime styles varying depending on the artist’s popularity, whether you want a background, how many characters, what type of shading etc. 
Prices are also higher for Episode covers because they’re considered “commercial” commissions rather than personal (which are cheaper).
But really good art will normally always be in the hundreds of dollars. 
Of course, there are some artists who charge a lot less and other who charge a lot more. I’ve paid an anime artists about $110-120 AUD for a 5 character artwork (it’s the price she asked for) and another artists who had a different style (and it was not realism nor semi-realism) wanted to charge me over $400 AUD for 2 characters and I decided I didn’t want to go through with it because the price was too high to me. 
Here’s a list I have of other artists’ Instagram pages and emails: