There were many reasons for the lack of knockoffs too.
First was sales, a high quality detailed mould was really expensive. If there wasn't a guarantee of selling millions of it, there's no doubt that the business would go bankrupt. There was no way these knockoff companies could invest that much money into it, nor could they sell that many.
Second was a problem with quality. Leggo had over seven thousand different parts with twelve different pipelines, the mould would cost anywhere from forty to two hundred thousand Euros to produce.
The error in the parts can't exceed one hundred of a centimeter, and there was a machine involved in testing if the parts fit well together, with less than twelve faulty parts per hundred thousand.
The maintenance team had to check around three hundred moulds a day. Taking the consideration of human hours and quality assurance, there was no way they could decrease the price.