A professionally illustrated book cover will cost, on average, somewhere between $500-$1,500. A fully illustrated book, as you’d expect, is much more expensive — more like $2,000-$10,000, depending on the scope and complexity of the illustrations. Pricing also varies based on the illustrator’s experience: a relative newcomer will typically be less expensive than a longtime veteran of the industry. If you have a limited budget for your illustrations, you might consider seeking out an illustrator who’s still early in their career, and therefore less likely to cost a lot of money.