I understand this is an old post but my 2 cents will be helpful for anyone who comes across this.
A mavic pro display model is just the shell with no electronics at all. The only usable parts are:
-The gimbal. It was fully operational on at least 3 display models that I have used for parts. Just install the ribbon cable, camera cable and a camera (dont forget to transfer the heat paste from the "old/damaged" gimbal into the display gimbal and voila it works)
-camera barrel shell, can be quite useful to put your camera board into if you have a scratched camera lens
-gimbal mount with anti-vibration rubbers
-all screws (except the board screws)
-the top and middle plastic shell
-the bottom aluminum heatsink shell
-arms (to transfer working undamaged existing parts from a broken arm, but requires lots of patience and is quite finicky especially for the front arms)
-gimbal bubble protector and gimbal buckle
-props
-motor prop springloaded holders and motor bearings. Other than these two things the actual motors are duds: The motor bell rotors have no magnets and the motor stators have no windings, and to be precise there are no stators at all installed. Its just the motor base and the magnetless rotor bell on these mavic pro display models.
-battery shell. It can be used to transfer existing battery innards (battery board and battery cells) to the display model shell if you have an existing scratched or otherwise cosmetically damaged battery that you want to make look brand spanking new again. Its a veeery finicky process as well as the one for the arms that I stated above and you have to be super careful opening up the old battery without puncturing or damaging the cells and board, and once you start you have to go through with it or else you will be left with a mangled battery, but it can be done, I have done it twice. Please note that this will not work for swollen batteries. Once you unpack a swollen battery it is almost impossible to repack into the display model battery shell, and in my opinion you shouldn't be messing with or flying with swollen batteries anyway
Nothing else on the display model can be of use for repair / spare parts, but thats a long list of usable parts that could run you at least $80-120 or more if you were to get them seperately.
So, to conclude, if you find a display model for around 20-40 bucks its a steal for all the parts you are getting, as long as you have the patience and knowledge to use them to repair a damaged mavic pro.
Happy flying