This type of glitch happens about every other week or so. I have seen the 5 highest rising and 5 lowest be the same thing. Jagex is fairly ftl most of the time.
A lot of people were selling their verac and guthan(maybe even other barrows pieces, don't know) for a price between low and mid, most of them even at low. Bought em, made sets out of them, took about 10k out of market price, and away they went.