Some people have an all inclusive dinner date package, and some people charge a part of the booking as social time. A lot of companions have social time rates that are very cheap, myself included. I've seen some companions offer 100$ for social time.
Another thing to remember is that not every SP wants to be taken to an extremely expensive restaurant for a dinner date. It's polite to book a good restaurant for sure, but if you don't want to spend as much, ask the person what they are comfortable with. I've had people book me for brunch dates, lunch, movies and coffee and drinks, they still paid my social rate, and it was cheaper for them. A lot of indy providers would not allow this tho so you have to be careful.