Hello i have lot of experience with creating illustration style and animation like that
So here my proposal:
1. 100$ / per character deisgn including all animation (idle, walk, attack, dead, etc..)
2. 50$ per background images (if needed)
3. 100$ all complete user interface (if needed)
4. 5$ per item illustration (if needed)
price is flexible according to what you need, just let me know if you need discuss something more detail :)