I just read this post and apologise for being a bit late to the party! I have a 2016 Q7 S Line 3 ltr v6 diesel that I purchased 8 months ago with 13400 genuine miles.
As the sat nav mapping and speed limits are well out of date I decided to update it, I asked my local dealer (Jardine) for a price. . . . . wait for it . . . . . £634, and there was me thinking I'd get change from £200! Had a look on ebay and found satnavishop.co.uk. For £79.99 I got 4 SD cards and 13 pages of instructions, I now have a fully updated 2025 satnav. It took me just over 3 hrs to install but I am getting on a bit and not so tech savvy so took things slowly as any mistakes can wreck the MMI unit.
Hope this info is of help someone.