That's exactly what happened to me on the early evening of January 3, 2015 at Cairo Airport Terminal 3 security check point, right before getting to the check-in area. One customs officer asked to see my bag because "you have a big bag, do you have a lot of money?", while another officer held my passport. My wallet emptied of my remaining two Egyptian bank notes. They never even looked for a split second into my bag even though I unlocked it for them. My bag was not even 20kg and not big in size. (It's a Burton Flight Deck if anybody cares to google the exact brand and model.) I passed the metal detector without triggering it and yet they demanded to frisk me. The whole set up of the x-ray and metal detectors really facilitate extortionists because there's a huge pillar right next to it. They put a table right behind the pillar so they can search (or pretend to search) your luggage on it, and that's where I was asked for payment. Right behind the pillar. I remember the officer used the word "baksheesh".

Without getting into a discussion of ethics, I was totally not expecting this as I never had officials asking me for money during my travels before. I was travelling solo, so maybe that increased the chance of encountering this hassle. My comments are not meant to offend any Egyptian, but I hope travelers be prepared, especially solo ones, of such occurrences.