Art for a game

You can browse the Professional Services category, it has a pretty wide swath of artists with varying prices.

$300 is actually pretty low for most professional artists, especially for a commercial product such as a gamebook cover. You’re paying for not only the time it takes for them to personally create the piece, but also the amount of practice and training that has gone into honing their skill level. If you aren’t able to pay for custom art, another user has compiled a list of stock art websites that can be used for free.