A few weeks ago my son attended a summer day-camp where they played with various kinds of robots. If I understood him the most interesting was the LEGO Mindstorms and of course he wants me to buy one for him. The problem is that it is very expensive (280 USD in the US + shipping)
or I might be able to buy in a local store but then I am sure it will be around 400-500 USD.

Besides the programming environment runs only on Windows and on Mac and we run Linux at home and only have Windows in a VirtualBox.

So I was wondering if there are cheaper alternatives, at least till I see that he is serious in playing with those robots.