I'm working on a project, a web app, where its success is driven by how well the information interacts and communicates with the user, which ultimately drives their decision.
The basic idea looks a little like this: the user selects an item and its quantity that affects the price they pay. That is the greater the number they select the better the unit price. To further help explain myself, imagine a user wanting to buy a Rolex watch priced $5K each. If the user bought one they'd pay a fixed price, $5K. However, if the user buys 5 Rolex's the unit price drops incrementally, i.e.
If the user buys:1 Rolex, they pay $5K (each) Buys 2 Rolex's, they pay $4.5K (each) Buys 3 Rolex's, they pay $3K (each) Buys 4 Rolex's, they pay $2K (each) or Buys 5 Rolex's, they pay $1K (each)
So, buying 5 Rolex's costs $3.1 each (a total price $15.5).
Possible solutions include a iPhone-like scroller or drop down box, both would display real time unit price depending on the quantity the user selects. This allows the user to 'play' with the quantities to see the changing unit prices before committing to a purchase. It's important all the pricing/quantity information is viewable before commitment is required.
I'm looking for design inspiration or examples in action that would help convey the benefit of quantity, but still give the user full control to make their own decisions.