You can disable it, actually.

Settings > General > AirDrop > turn off Use Cellular Data

That said, I don’t really see why you would disable that. It’s only a backup method for when the peer-to-peer connection fails. Unless you are sending huge files on a regular basis, I wouldn’t expect it to be worth disabling. Also, most metered plans I’ve encountered just cause your connection to be very slow after you hit the data cap.

If you are on a plan that automatically charges you excessive overage fees without warning and there is no other choice, then my condolences.

Oh, cool, thank you! I must have used the wrong search terms; I could only find vague hints about deactivating Handoff/Continuity.

I stand corrected, and I appreciate that Apple did consider the non-Bay-Area use case :)

> Unless you are sending huge files on a regular basis

I do use AirDrop extensively for sharing photos when traveling. One sharing session could easily eat through my roaming allowance.