As soon as the customer intimated it wouldn’t take long, alarm bells would be ringing. Put in a quote based on how long it will take you multiplied by an hourly rate over and above what you achieve for window cleaning as this will be harder work. Then tell the customer to feel free to obtain other quotes, if someone is cheaper than you, let them do it. Personally I would Price it not to get the job, all these apex’s look like a ballache.