How much should you pay a friend for a service they rendered you?

I’ve had a friend design a website for me.
He’s in web design part time for himself, and he said this project took him about 5 hours. Now normally he would charge around $200—$250 for client work but would charge me less. I asked him about payment and he was under the impression he was doing this as a favor. I am certainly grateful, but I know he is somewhat struggling financially to find adequate work to support himself, and I know he dropped everything he was doing to help me with this as I needed a fast turnaround.

We were roommates and still remain good friends.

My question is what is appropriate amount to pay him? Keep in mind this is a business expense so tax-wise it is written off. I really would like to pay him something for his time (or maybe get him a gift?), but I also understand maybe he would like to do this as a favor for me based on our friendship.
What do you think?