The feature requests you have made are relatively simple to implement in drupal. By your statements, I am assuming you already have a theme styled and ready to be implemented? I honestly do not feel that your website should cost any more than what your reasonable budget is allotting, and as such, feel that $750 dollars is more than reasonable to accomplish this task.
I believe that all websites are pieces of art, and as such strive to provide just that - art. Let me know if I can help you on this project.