It was wrong. Morally and legally. Jim Gunn and other said it above.
I must be an expert legal adviser...because I've seen those judge shows on TV many times
But I've learned by that they basically entered into a contract, by agreeing to do xxx for $$$ at said place and time. When THEY broke they contract, they are liable for some lost $$. There would be no "kill fee" if it weren't morally and legally proper.
I completely understand casting or a look-see to see if the girl looks anything like the description. I bought lunch for a group I had to turn away on those conditions. The agent somewhat assured them of work, but they weren't in my niche (aka too old and unattractive). Smokie explained this was not a casting or application or interview, that had already been completed earlier, and they provided a job offer which she went to. Yes no doubt whatsoever she is entitled to some amount of kill fee $. If e.g. they apologized and re-booked her for the next day it would still suck, but might lessen their moral and legal obligations to $.
Producers who don't agree are wrong. Those who didn't understand the scenario should have read more before passing judgment.
On the flip side, yes, it is too bad producers can't easily collect from the models that also enter into those contracts and f^k us over by no show, being drunk etc. Somehow I don't imagine many judges having sympathy for the producers cases though.