We don't spend a lot on kids' activities (like sports or music lessons).
Over the last year, we have spent money on kids as follows:
Summer camp - $53/wk all day camp offered by the city parks and rec. 3 weeks x 2 kids. They go swimming 1x week and a field trip 1x week.
Roller skating - $4 for a 3 hour session. We go with friends. Maybe 6 times in the last year. No lessons, they learned on their own with a few tips from me.
Swimming - we bought a 30 admission punch pass for the kids and adults. $60 or so. We try to go once a month to the city's water park. It's probably more like every other month. We did lessons in the past (one kid passed, the other failed).
Engineering after school program - build robots and rockets and stuff like that - $5 for 6 weeks.
That adds up to maybe $450 per year.
You might note that we skipped organized sports, dance, cheerleading, ballet, gymnastics, and music lessons. The kids stay pretty busy with the activities we already pay for, and we do plenty of other typically free things, too (museums, parks, tennis at the parks, hikes, backyard campfires, visiting friends, playing outside, play dates, library, travel). How do families have time for all those other organized activities?
The odds of my kids ever being professional athletes or well-paid musicians is pretty low. I suppose I could step up the outlays and spend a ton of money in the hopes that I would find the right activity to enroll my kid in, and hope they enjoyed it and excelled at it. I just figure with all the free or cheap alternatives, they'll get enjoyment out of life with the options they have available today.
We might put them in soccer or martial arts at the rec center, as these classes tend to be moderately priced and they can walk to the activities.
How much you spend on your kids for classes and activities is a personal question. I tend to fall on the side of "there's too many free skills and activities that are just as important as the paid activities". My kids like painting, paper crafting, sewing, and fashion design, for example (which happen to all be free or dirt cheap). If I put them in organized activities all the time, they would spend little time on their current interests and a lot more playing travel soccer, or swim team or whatever I stick them in. Would that enhance their skill set, make them more employable one day, or boost their quality of life or enjoyment? I don't think so, but I understand if some disagree.