At approximately 14:00 Ethan refers to his guitar as his grandfather's Martin. The guitar he is playing is in fact a Martin guitar worth thousands of dollars. At approximately 1:13:30 when Adrienne smashes Ethans guitar it's a cheap Rogue guitar which is only valued at one to two hundred dollars. Also, in the close up shot of the guitar hitting the wall, the guitar's headstock is already broken off before it hits the wall, indicating that they used the already damaged guitar from the long shot.