So something to consider here: There are absolutely windows where doing something for "exposure" is worthwhile. Evaluating those windows intelligently is what matters.
Case in point. I barely made any money doing 20 hours+ a week broadcasting Overwatch community tournaments for the better part of 7 months or so. However, I knew that I'd be building skills and a brand in a field where being in early mattered very much. As a result, it gave me a strong resume to do things like broadcast for TBS on ELEAGUE, or work events like Blizzcon (events that of course had very competitive pay).
If I took the hardline approach of wanting top tier caster rates from Day 1 (For small 120-500 dollar tournaments) not only would I not have gotten those rates, but I wouldn't have had incredible opportunities come to me later.
The main thing is to evaluate every situation and realize that if you do work for less, seeing if there is a bigger plan or more tangible goal that it will actually work into. It's not black and white as some people paint it in this thread.
There is a difference between this, and most of the requests that people are talking about in this thread.
It's all a manner of scope and scale.
In your case, you were working for amateur events and getting amateur pay. Nothing wrong with that. If TBS was asking you to work for free though, that would be an example of the topic at hand.
One of my personal examples (I've got more than a few) was with a contract for a VR company in the Valley. They were doing work on eye tracking and wanted a fully documented SDK assembled in 2-3 weeks.
We had discussed rates, scope of work, and expected start date when I was told one of the co-founders wanted to have a chat before committing.
Nice enough guy, but halfway thru the conv he switched into whining about costs, how they can't afford to pay for documentation work since they pay their coders so much, and why can't I just do this one project for stupid cheap (way below my normal rate) and then they could "give me more work in the future."
At that point I politely declined and wished them luck in finding someone with the experience to do what they wanted at the price they were offering. I never did find out if they got their SDK ready for the big event they had planned.