Re: The cost!!
Flying lego: https://www.popularmechanics.com/flight/a23667/lego-plane-that-can-fly/
Some of the cheap alternatives are so bad that you can put one piece on top of another, pick up the assembly by the top piece, and the bottom piece stays behind. The tolerances that Lego is made to really are very tight, but they have had a lot of practice at making blocks by now and I don't think the price premium is completely justified by that alone.