A non-Lego system brick has got to be pretty old before I don't mix it in with everything else. You know the sort; the plastic feels off, it doesn't have the same grip, the colours are kind of weird.

Nowadays it's all pretty much the same and even Lego ain't what it used to be. They have some new formulation that doesn't grip as well. If it isn't ABS, it's not going to work as well.

I aim for about $AU25 a kilo on bulk used Lego. If the seller's pictures show some good stuff, maybe more, if it's all basic bricks, maybe less.

And sometimes people just put a price on a tub without any real idea of what it's worth. Always worth looking for bargains and snapping them up.

The downside is washing and sorting. That gets old pretty fast.