Yes the discussions and debates do help. But this can also be had today with high quality forums (e.g. HN forum, google groups etc).
>>Many 'great thinkers' cannot just be picked up off the shelf.
That's where a little bit of internet literacy (mainly the google-fu skills) helps a lot. It's not that difficult to acquire it either. If you acquire these skills (e.g. in your high school) then finding great thinkers is not so much of a problem.
In fact, I did it exactly in such a manner: I am from a third world Asian country, where such great professors are mostly non-existent or if they do exist they are almost always inaccessible to poor people like me. So, what did I do?
I struggled with Google for some time, and with the help of some sites I acquired the immensely important google-fu skills. Then I landed on the Wikipedia knowledge-galaxy. From there the access to 'great thinkers' was just a click away.
As far as discussions and debates are concerned, then I read books presenting opposing views on important issues like religion, economics and politics.
e.g. In case of religion the theists' point of views, Bible, Quran etc on one hand and Plato's dialogues, Darwin's theory, Voltaire, Khalil Jibran, Richard Dawkins, Sam Harris on the other hand;
Marx's Das Capital and communist manifesto on one hand and criticism of Marx and Atlas Shrugged on the other.
I engage in online debates on forums like this.
Thanks to today's internet and the sites like the ones I mentioned in the earlier comment on this thread, a person who has far less money than $200K (hardly $2500 per year) can actually acquire so much knowledge.
It's not bragging though, as the same knowledge has made me more humbled too.