Here's how to change your chart labels from actual data to something like $1K.
Apply it by right-clicking the data label and going to the number tab, then in the Custom category. Type $0,"k" in the "type" box and hit OK.
[If using Microsoft 2007, then click on the "Format" tab, "Format Selection", "Number" and then type into "Format Code" box: $0,"k".]
Jon Peltier (first link below) has a great page of information about number formats, and he spells out thousands, millions, etc., specifically toward the bottom of the page. The Office Online article will also give you a good overview so you can understand what's going on with the dollar sign and the K inside quotation marks. Thanks to Echo S.