Is there anything compatible with meccano but cheaper?

[LaBelleDameSansPatience]

DD (6) suddenly into meccano. We have a small box of odd pieces and need some more, but it is so expensive! Was wondering if there is anything which is cheaper but would fit with it, like some of the lego-alikes you can find.

[xalyssx]

My boyfriend works in a toy shop and unfortunately he has never come across any, sorry