No two illustration jobs are exactly alike. I will quote you a price based on your requirements, the type of art requested, circulation, size and other factors. I can give you some general pricing ideas though
Book and book cover illustration
Paperback book cover, front only: $960-1440
Paperback book cover with spine wraparound: $1200-1680
Paperback book cover with full wraparound: $1440-1980
Book jacket, front only: $1200-1800
Book jacket with spine wraparound: $1680-2400
Book jacket with full wraparound: $1800-3200
Interior illustration, spot drawing or chapter heading: $60-120
Interior illustration, half page: $240-480
Interior illustration, full page: $360-780
Interior illustration, 2-page spread: $720-1200
Children's Book illustration -Advance: $2400-4800 - Royalty: 3-6%
Stylized illustration & iconography:
Stylized representation of your subject or item: $240-480 per image
Icon sets for apps or interfaces: $120-240 per image
Product illustration
Depends on complexity of your product depiction: $240<