When I have spoken at conferences, usually the pass is for the whole event, and you are right that this could sometimes be multiple thousands of dollars, so it is a good way for me to get to these conferences and hear other speakers without my employer having to pay a lot for my personal development. And, usually, there will be a speakers dinner or after-party during the conference, which is a great way to meet and talk with other like minded people in your field. But, it can be hard work - even for a 5-minute lightning talk, the amount of preparation is vastly out of proportion to the 'live' time in front of an audience, however it is definitely worth it.

At the beginning of my career I would never have thought it would be something I would be doing, but if your work is interesting then it should be interesting and informative to tell people about it, which is all one of these talks really is, at base...