Designing a book cover

I am going to be publishing some of my stories and was wondering about book covers. So far I have been using pictures that I have found on unsplash and I have been pretty happy with them, but, if it wasn't too expensive I thought it might look even better with someone who was more artistic designing them. So... does anyone know how much that costs and who would be a good collaborator?

Thanks in advance
Hugs
Savannah