Does Speech Therapy Work?

I admit, I was skeptical about speech therapy.  With my son J speaking very little and quite behind on his vocabulary as well as showing no interest in letters or words, I finally gave in to my anxieties and got him to see a speech pathologist.

Firstly, they're not cheap.  The one I see costs $70 for a half hour session.  The initial assessment cost me $180.  And of course, I didn't take all those extras on my health insurance so it's all out of my pocket... sigh.

The first time I went, I watched what they did with my son.  The speech pathologist tried to talk to my son and play with him, and on subsequent sessions, it looked like all she was doing was playing with my son with toys.  The toys themselves have purpose of course - lots of Mr Potato heads so that body parts can be learnt; a shape sorter so he can learn shapes and colours as the blocks are coloured; one of those pop up pirate games where you insert the swords into slots on the side of the barrel (though I'm not sure what this is for, maybe for learning to take turns and learn colours); and a box of toy foods obviously for learning everyday foods.

However, for whatever reason, his speech has improved.  I haven't really done much homework with my son J, because it's a little advanced for his current comprehension level, but I am trying hard to focus with colours and talk to him as much as possible.  I was doing that before though, and not with much success.

People have said they can understand him more now.  He consistently does 3 words, and he is intelligible.  He talks a lot more and he greets everyone and says goodbye properly with names.

I wonder if I had done no interventions, would he naturally develop his speech?  Many people have said to me how they know someone who didn't speak till they were 5, or how Einstein didn't speak till late... however, how long would I wait?  I waited this long, and saw many of my friends taking their children to see Speech pathology at a much earlier age because they were concerned.  But, I console myself by thinking, that if I did nothing and it was too late for early intervention I would be kicking myself.  So, it hasn't hurt my son at all to go to speech therapy - he thinks it's a new game, and quite enjoys going.

I don't know how long I need to persist with speech therapy.  Perhaps until he is fluent or speaking in sentences.  I chose a speech path that is very far from my home, near my work, because it was recommended by friends.  It sucks up a lot of time for me, and though it has done good for my son, I won't be sad when I don't have to do that long ass drive anymore!