DD is a teen now but has tried lots of clubs over the years.
Dance, drama and singing, we did an unlimited classes deal I think it was £28 a week but she did ALOT of classes (costumes, shoes, other expenses not included) - most expensive hobby costs completely spirals avoid unless your child loves it.
Swimming lessons £7 an hour, group session
Swimming Club £30 a month, could swim up to 6 times a week (insurances, race fees etc not included race costumes are expensive)
Recreational tennis £6 an hour + own racket
Horse riding £23 an hour - did a 6 week course enjoyable but she didn't love it.
Rugby £90 a year, only have to provide your own boots, socks, shorts and mouth guard. - Best value by a mile, everything else is included including post match food and minibus travel to matches.