I don't think you can put a price on it. The price is dictated more by the context than the resulting mockup.

In one context someone might have paid a few thousand for this design. In another, a few hundred. It is valuable as a solution to a problem, so asking how much it is 'worth' is like asking the value of a chess move. Again, it's all about the context.

What I can say is that I know of designers charging AU$50/h for work of a seemingly similar quality.