I remember my last kids bike before getting a grown up one (infact I grew so quickly I think I went from 24″ wheels to a 21″ frame!).
Diamond Back, 4130 frame and forks, shimano group-set of some description, relatively light. But even with inflation it wasn’t £1500!
I can see why it’s £1500, but it seems a lot of ££££ for a bike that at 12-13 they’ll outgrow in a matter of months.
Sailing has the right idea, most ‘youth’ classes are either older and un-cool (Mirror), or roto-moulded plastic (RS Tera/Feva) with cheap sails and hulls. I guess Isla bikes are for mountainbikers who if they sailed would buy their kids a 29er (the boat, not the bikes).