Generally, the prices are:
Characters: 15-20$ - simple pixelart
25-50$+ - higher resolution or more complex animation
Backgrounds: 20$ - simple, small amount of objects, no deep perspective
30-45$ - medium, perspective, of many objects, different planes like in parallax effect.
60$ - and more for complex, long time work
Tiles: 25-30$ - for a basic set, and more for more complex assets.
Props: 1-2$ - for a pixel item or spell pictures etc.
I can find solutions for your budget, if you have any questions, please, write me:
simulya2007@yandex.ru