Depends on where you play and what game you are playing. My college arcade had games that cost one token and you could buy 5 tokens for a dollar (but most games cost more than one token). Pool cost $2.50 an hour with membership. There are also games that cost $3 or more depending on what arcade you are at and what game you are playing. based on time, barbox pool is probably cheaper considering beginners might take an hour to finish a rack.
If you are trying to figure out why kids play video games instead of pool, you might also want to take into account that arcades are dying faster than pool halls nowadays. 95% of gaming is now done at home.