The average cost to go to a basketball game really depends on where you're sitting, what you're buying, and where you're parking. Back during the 2015/2016 NBA season the most expensive average ticket price to go to a game was a Knicks game which was $129.38. During the same season the cheapest average price to go to a game was a Pelican's game which was only $30.20. The mean cost to go to a basketball game was roughly 52.80. But once you add other expenses like parking and food, your total can be all the way up to $60 for only one person if you are paying for the mean ticket cost.
Now some people would rather play the sport than watch it, which can cost different prices depending on what you want to get. You need a ball which can cost $15-20 depending on what ball you want. Next you need some shoes which can cost from $105 to $220 depending on what you want to play in. Next you need a basket (which you can go to the park for and play with for free) which can cost from $100 to $200 for one that is moveable and from $300 to more than $1000 dollars from on that goes in the ground. There are also some other items you might want like a waterbottle or headbands which typically aren't more than $5.