No, you didn't mislead him, and rightfully, he should have mentioned that little detail, but he chose not to. The reason, I believe, because it works most of the time. People that do this, know ahead of time they will use a super low priced service to get through the door, and then drop an upcharge after getting all set up, and beginning the work. 95% of the time, people with just figure it's their dumb luck that the project will cost a lot more than anticipated, and pay the upcharge. You did the correct thing by sending him on his way, IMO.