I was newly certified to be diving normoxic trimix, and I was going to Florida for a vacation. I was hoping to get in a tech dive while there. The course director at my Colorado shop had worked for a shop in Fort Lauderdale in the past, and he knew a tech diver (instructor) there. He thought the guy might want to do a dive with me, and he got me the guy's email address. I wrote to him, telling him the circumstances and asking if he would be willing to do a tech dive with me. He said he would.
He set everything up--chartered a boat, got me tank rentals, and got us both expensive trimix and deco gas fills. It was not until we were getting on the boat and it was time to pay up that I realized he expected me to pay for everything--my tank rentals, my trimix fills, his trimix fills, my deco tank rentals, both of our deco gases, and the full cost of the boat charter. He was acting as my guide, so I had to pay everything. I checked my email later--there is no hint in there that I was asking for anything other than a dive buddy. In fact, it was pretty damn clear. I found out later that the tanks I rented were all his, so he was charging me for renting his tanks, too. I was too meek and timid to protest, and it is damn lucky that I had a wallet with a bunch of hundreds in it to pay for it all.
While we were diving the wreck of the Hydro Atlantic, he signaled me to ask how much gas I had. I signaled back, showing that I still had plenty to continue the dive. He immediately thumbed the dive. When I asked later why, he said he did not know me and had no idea what my gas consumption would be, so he had thumbed early. When we got out of the water, I still had more than half of my trimix remaining, and I am sure he had more than that. So I paid many hundreds of dollars for a short tech dive to about 160 feet. My friendly "buddy" got a free dive and went home with hundreds of dollars of gas that I paid for left over for his future diving pleasure.