UPDATE: Although a confessing capitalist, I acknowledge that not everyone has the same chances and opportunities in life. (and this I know because I'm a nearly-deaf freelancer who can't telephone with clients, doesn't understand presentations, speeches, or video tutorials and has a hard time understanding anyone in social settings.)
It's a fact that an individual is often powerless to get the work they want in situations where that work is simply not reasonably compensated. This is not a fault of our own -- even when we reject that kind of work, others will happily accept it and make low rates the standard.
My point is that even then we should not be inactive, but always look for new ways to use our skills to make a living. We are experts at what we do, after all.
This is why we need groups like ArtPACT that educate and inform about the industry, and illustrators' guilds like the IO (in Germany), the GAG, AIGA, and AOI to educate ourselves about legal practices, business standards, industry rates, and support each other, because we are stronger in numbers.
When you are a freelancer complaining about low pay from a client, you are essentially saying:
I am willing to work even for payment that I do not consider appropiate → thus I don't care what I am paid.
I don't discuss money with a client, or don't agree on a mutually acceptable fee before starting work.
I blame my clients for not quoting reasonable budgets instead of quoting my own prices or declining a job.
You may have taken on underpaid work as a beginner (like I did) and only in retrospect realized it for what it was. Or you might accept these jobs even now because a little money is still better than nothing.
But then …
… stand behind what you do, or once did. Never blame „the industry“, or your client, or anyone else. It is your choice alone – nobody is forcing the underpaid job on you!
It is in your power to negotiate, decline a job, demand your own price – always. Accepting a job and then even only mentioning „low pay“ is unfair towards the client who thought you were 100% fine with what you both agreed on. It puts them in an awkward spot and makes them wonder if you're gonna complain about them to others, or what else there might be that you're not OK with and haven't mentioned yet.
Do take on underpaid work if you really want it, but know what you are doing and why. Hold yourself responsible.
In the end it is up to us, the freelancers, to create acceptable industry pay standards.
NOTE: Of course it is important to point out and discuss detoriated pay standards in our business in general
, and to identify reasons and solutions for that.