A friend does talks & demos (about a hobby interest), usually at a set fee + travel.
Whilst on holiday, the friend bumped into an acquaintance/professional contact who said it'd be great if they could set up delivery of a talk to 'his' group. Professional contact ("PC") has since been in touch to arrange dates, etc. PC works for a pretty prestigious organisation. After a little exchange of emails, everything is sorted & booked in for X date at X time. However, contact has signed off the message confirming booking, "...as agreed, your fee will be £££ + travel expenses."
This is the tricky bit. £££ is not friend's fee rate. It is substantially more. Friend would not have quoted this amount.
Friend will be travelling approx 1hr each way and will be delivering a three-hour talk.
Does friend reply to simply confirm everything? Does friend reply but query fee? Does friend reply but acknowledge generous fee?