There's no way that NADA can have an accurate clue on true Griso values. Their numbers are based on transactional data. That's easy to establish on automobiles...a bit harder on motorcycles...and essentially impossible for Moto Guzzi. The numbers they publish on something as thin-on-the-ground as a 2007 Griso is purely an educated guesstimate.
Want to know how I know? Because on various occasions they've asked me to review their data!
SR