I don't agree with the highlighted part of this statement or think it makes any sense. Unless you are gambling in a Vegas casino, you aren't going to get good returns on anything in less than two years. Really, unless your timeline is five years or more, you aren't really investing. You are just speculating. And I'm not just talking about Lego's here, I'm talking about any investment. If you invest in the stock market (which I do through my 401(k)), you should plan on having a five year timeframe at least if you want pretty good chance of getting a return. It takes time for companies you hold stock in to improve their performance, and sometimes there are market downturns, etc, so you have to have a long term timeframe in order to invest successfully in stocks/mutual funds.
So this idea of "Why would you invest in Legos and wait for a couple years to see the margin you see... why not invest elsewhere?" doesn't make sense. You can't invest elsewhere in less than two years. You can only gamble elsewhere in less than two years. Real investing takes time and patience.
And as far as the economy being on the upturn goes, that's pretty debatable. For most people the US economy is still in the toilet. Lego investors are fortunate that our target audience of "Rich AFOLs" has been doing better, which helps us, but in general things aren't better. For example, Walmart just released an investor statement saying that their lower to middle income demographic is still doing badly, which has hurt their results. So a lot of companies you might invest in, especially those catering to the broader segments of the US economy, are still not doing well and that can certainly hurt performance of other investments.
So in summary... there's no free investment lunch anywhere. I have both Lego and stock/mutual fund investments, and I have long time frames. That is really the only way to go unless you want to gamble.