Only one of these type of things (that wasn’t church/volunteer based) I’ve known survive was run by two friends. They had a messy play area but also a lot of toys, a bouncy castle, soft play stuff, ride on toys, bubbles, a water table, craft area, playdough table etc. They appealed to babies, toddlers and preschoolers - lots of SAHM, nannies and childminders went because they could bring all their kids rather than just a baby to a baby class.
It went to a different village hall every weekday and they hired all the equipment out for birthday parties on weekends. Cost was about £3 for a village hall session on a drop in basis, and there’d be maybe 40 families there over the course of a morning, plus they’d sell snacks and drinks. Birthday party hire was individually priced so I don’t know what that cost.
I got chatting to one of them once and they worked monumentally hard - driving all over the county, loading and unloading the van, setting up, cleaning up, taking money, selling snacks and drinks, buying materials, loads of marketing and social media, all the legal and financial side (insurance, accounting, tax, health and safety, training, van maintenance, equipment maintenance…). They worked 6 or 7 days a week. It kept going for absolutely years until covid hit so they must have made something but I doubt it was a massive money spinner.
There must be easier ways to make money OP.