The price will be quite low:
1 Teensy-LC 12 USD
2 SD connectors 6 USD
1 USB connector 2 USD
few other components as wires, resistors, etc. 0-5 USD
3D printed box - I have my own 3D printer...
Stuck on a island in the middle of the ocean without a wifi backup disk?
The TEENSY SD USB back up tool is what you need!