Received my PortaPros today and so far I have to say, they're pretty impressive considering their size. I probably wouldn't pay more than $40 for them, though. I'm definitely more of a closed-back headphones type of person, and the PortaPros just don't produce the kind of fidelity that I'm used to. Bass is very good for headphones of this type, but the highs seemed a little...off. They sound a lot better with an EQ, IMO..
EDIT: After a few weeks of listening, I'm extremely satisfied with the PortaPros. I would gladly pay $40 for another pair!