I don't think I have ever paid for anything over a few hundred in cash. Criminalising the use of cash seems a bit authoritarian, but I don't think there is any legitimate reason to pay for anything in cash with that amount that couldn't be done by a BACS transfer.

In the UK you have to register with HMRC under money laundering supervision regulations if you are a business or trader that takes in cash payments over 10,000 euro.