I now own my own boat that used to be my father-in-law's. When he bought it 10 years ago, he bought it direct through Hyde. They took him down a river once when he bought it I guess you could call it a lesson), but I am not sure whether he paid extra for this or not. They also included an instructional video on how to row a drift boat.
Having floating many, many times prior to him buying the boat (both in my uncle's boat, and with guides), and having watched and listened to several different guides, I took the oarsman's seat for the first time in my F-I-L's boat with only the knowledge of how it was supposed to be done.
It seemed like it wasn't too hard to pick up, and as usual, experience is worth way more than just the knowledge.
Personally, I wouldn't pay for lessons unless I had just bought a brand new $8,000+ boat and had never rowed it before. It worked for me, but I also learned on the Green in Utah, which isn't the hardest river to row by a long shot.
I don't see any reason not to offer lessons. There's certainly not much to lose.
"Engineers don't idle well."