The lift is very handy. I used a Gil-Lift on a multi unit kitchen project a few years back. With the right install strategy they make things very quick and simple. I couldn't justify the cost of buying a new one to my internal bean counter and I couldn't find one used so using a photo essay on Woodweb as inspiration I built my own. The winch, casters, and other misc parts and hardware set me back less than $100 and the ply and hardwoods are drops. The build took less than a day and was fun.
When pricing the potential job that your customer mentioned it would probably be wise to allow for extra time for the build. Some of the materials can be all over the place and difficult to tame. It would also be a good idea to request samples so that you can see what you are up against and so that the customer can see what they will actually be getting. Some of the wood can be pretty bold as far as grain, imperfections (character), and colors.