You may have a slight overexposure on the hands. This could be as a result of the black of the machine causing your camera to compensate for what it belives to be a dark scene
A frustrating situation, recognized by all. lots of money, but not ON you. A little soft on focus, composition is busy - maybe cropped in to the hands and the change slot ?
Technical: Fits the challenge. Exposure looks just a tiny bit too bright. Composition is relatively good if maybe a little too busy. Focus is good. Lighting is even.
Personal: Good idea, perhaps shot a few more ways would yield a stronger photo.
Ha, I like it! You went a little further with the basic idea than most and I think made a good statement about money in the modern world with all those other paper and plastic "sometimes" accepted forms of money exchange.
i am sorry, but i do see the "likeness of real currency" on top of the coke machine, and they specifically asked us not to include it... i am not going to rate this photograph.