Pressure Washing Contractor

I'd like some input: A friend installed and finished 22 drywall sheets for me. I purchased all materials, and he quoted $1,000 cash for labor. Was that a reasonable price for the work performed, and would it be customary to add a tip?

This enclosure seems like it will restrict airflow. Thoughts? pix of our friend's new A/C enclosure. I'm thinking it's a tad restrictive. I estimate it's 3-4" distance between wood slats and fins. Back portion is about 8" to house.