I'm away on 6th Dec, but the last time I gave a presentation at a Sarf'En flying club, all I asked for was petrol costs, light meal and overnight at the Premier Inn.
£2500? Ridiculous. I'm also interested to know why the SR-71 pilot was deemed 'too expensive' - if it's the same person (an author keen to flog his books...) who gave a chat at an aerodrome near Maidenhead last year, then I wouldn't bother going even if it was free. His talk was pretty well pre-scripted and aimed at completely the wrong audience...