Dropping someone at a UK airport? On average, expect to pay around £6.51, but...

https://jeffreysbestjournal.opalvector.com/posts/what-should-i-check-before-i-rely-on-a-free-long-stay-drop-off-window

Dropping someone at a UK airport? On average, expect to pay around £6.51, but it’s closer to £10 at Gatwick and £7 at Heathrow