The graph shows the relationship between product prices and the revenue gained from those products.
The Y Axis (labeled "Full Product Price") shows various prices at which your products have been bought. For each price point, the X Axis (labeled "Total Revenue") shows the total revenue that was derived from products that had that price. (As with all Analytics pages, this graph includes only sales that were made in the selected time range.)
If you've sold products using a discount (in a Sales Campaign) then the revenue bars will be subdivided to show how much revenue was made at each discount level.
There are a couple of things worth noting about the price points that are shown on the Y Axis. First, these are the full product prices, i.e. before discounts. Second, the product prices are all converted to USD, for easy comparison. So for example, if you had a product with a price of 300 KC then it will show up in this graph under the price "$1.00", because 300 KC = $1.00.
The graph shows at most 20 price points. If you've sold products at more price points than that then only the 20 price points that produced the most revenue are shown. The accompanying table (see below) does show the full data about all the sales you've made.
Revenue Per Product Price (Table)
Below the graph there's a table that contains the same information as the graph, but in a more detailed form. First, the table shows all the price points where products have been sold (the graph shows at most 20 price points). Second, the table shows the revenue for each discount level separately (the graph stacks them together into a single bar).