I don't have any great vision for what 4000 sq ft looks like, but I recently got an estimate for replacing my driveway and it was $8000, so the $9000 sounds in the right ballpark.
I'm having mine replaced in the spring because not only is it kind of a mess, being 55 years old, but the ground has settled enough that it drains the rain water towards the house and not away. It hasn't been a top priority, but it does need doing and will make the exterior look a lot better. However, I'm not planning to sell my house, and don't think of it as an "investment".