It occurred to me, as I was angrily shredding junk mail, that the issue here is actually the difference in mindset between the hobbyist/part-timer working for fun money or to supplement a full-time brick and mortar wage, and the full-time freelancer who approaches Turk from more of a business mindset (which may be you as well, I don't believe I've made your acquaintance as yet)
Not only does it feel like an unacceptable risk to continue to work for someone who has proved that they'll drastically cut my pay without warning or reason, *I can't afford* to subsidize them by spending too much time figuring out how to adapt to their lower pay - which in itself has an additional cost for me. If I'm going to spend what little spare time I have doing anything, it'll be finding someone who will pay me decently - which has a clearer and usually (in my experience) much quicker path to success.
I guess if your rent payment isn't hanging in the balance, you wouldn't care as much about stuff like that. Apologies, not sure why that took so long for me to realize.