Typically there is no extra cost for bringing in something to be color matched and having the paint store create a custom color for you. The spectrophotometer digitally scans your object and records the reflected light wavelengths to create a color formula. The House Beautiful article says that spectrophotometers struggle with metallic objects, objects that are smaller than the size of a quarter, and photographs. Otherwise all else is game!
If you can't bring your inspiring object to the store and you've got some extra cash at your disposal you could buy Benjamin Moore's handheld device for $299.00. However this device will only tell you the closest existing Benjamin Moore color; it can't create a custom color for you the way a spectrophotometer can. Also check out this AT LA post about another handheld color matching machine.
Have you tried bringing in objects to be color matched? Were you successful?
Image: Flickr member Nick See licensed under Creative Commons