The first few years I hated this for exactly the reasons you mention, but now I'm just happy they are happy. I think I have a few more years left before they don't want to go rubber ducky fishing with their dad no more and I doubt by then €20 gets me 2 minutes of joy with them.
It's like video game arcades. When you had to pay to play for 2 minutes, it was way more exciting than now playing in an emulator
As an adult, if I went and they said it cost 0€, I think I'd play too.
The reward of a game is playing it, not the 'prize', although that can add to the enjoyment too.
Oh yes, I got it, they are like the claw machines that have fake bills and iPhones with them (at least that's what I saw too).
But the point of having fun, you know it's a rigged game.
You can just say no. I have never played a single one of those types of games in my life because once I was old enough to work I understood my parents point of view. I'm actually thankful for them teaching me these sorts of lessons no matter how much I hated at the time. It's actually okay to not allow your children participate in cons and scams.
which lesson is it exactly?
2.) Something being fun but expensive is skippable and it is good to be able to say "no" to expensive fun.