HOLY SHMIT! That guy is trying to rip you off. So long as the ribbon cable for your camera hasnt become damaged you only need to replace the camera yaw motor, it’s like 20 bucks online. This is the one i bought to fix mine https://www.ebay.com/itm/OEM-Gimbal-Yaw-Motor-new-version-for-DJI-Phantom-4-4-Pro/133029969718?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
The repair can be a scary task but the internet has all the answers you need. If you need the ribbon cable make sure you get one for the P4P because the non pro uses a different cable, i went with this one https://www.ebay.com/itm/New-For-DJI-Phantom-4-Pro-Flexible-Gimbal-Flat-Ribbon-Flex-Cable-Spare-Part/223085524510?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
I know this is a super late reply so let us know what you went with.