Where I think this analysis is wrong is using the general inflation number. If your inflation basket of goods was full of products similar to Lego – plastic toys – the real price of Lego would not appear to be going down. Well, "wrong" isn't perhaps the right word, but it doesn't address the perceived price of Legos in a world where plastic goods are constantly going down in price relative to other goods.
Exactly. Pace the article, the reason that Lego seems expensive to us is that other toys are now much cheaper (in real terms) than they were in the '70s. If you corrected for "toy inflation" instead of "general inflation" this would be apparent.