Is $8,000 to repair cast iron sewer line with epoxy a fair price?

We hired a contractor to replace our old cast iron sewer line and install double clean outs between our house and the city sewer. He excavated and then decided it would be too involved and undermine the foundation to replace the cast iron so he was going to shoot a liner through the pipe. We left for a week and came back and he told us he didn't shoot a liner but did something with epoxy. When he put a camera down and showed us what he did, it showed that this epoxy does not go the whole way around the pipe. There was a layer of epoxy in the bottom of the pipe (the flow line for sewage water) but nothing covering the top of the pipe. The contractor says this is fine as long as the flow line has a new lining but that seems like BS to me. All of the sewer line repair research I've done shows that whether they shoot a liner or do a spray liner, it coats the entire pipe. I feel like this guy is scamming me and at the very least i do not want to pay the 8K he quoted me. His work seems like a shitty band aid and that I'm going to need to bring someone in to re-line this pipe 5 or 10 years down the road. Am I out of line to think this guy did some seriously shoddy work? He basically just poured some epoxy down my sewer and called it a day