I'm working on a white tile roof at the moment that is worse than yours as far as coating damage and algae growth is concerned. I told him ahead of time that the entire roof will never be bright white again, but that a cleaning would help preserve the coating that is remaining, and it will still look quite a bit better than not cleaning it at all. As I've learned on here from all the guys with experience, set their expectations right, and honesty will sell the jobs.

Ethan, out here in southern California these kinds of tile roofs own the majority, so we've cleaned quite a few. I agree with the fairly obvious (stated already) that something, whether it be time, weather, pressure washer, etc. has worn off a good amount of the outer coating on those tiles (you can see what they originally looked like by looking at the new/replacements on the roof section in your first photo). This isn't something that a SoftWash will reverse, but it does look like there is enough growth up there to warrant a treatment, and it will probably look a little better.

If I were you I would show those photos to your customer and allow him/her to see more closely what is truly going on up there. Point out the things you can improve with a SoftWash and the things that will remain the same even after a SoftWash. Those are nice clear pictures so it should be easy to see. From there I would let them weigh out whether or not it is still worth it for them to have you clean it. Either way you'll establish yourself as an expert in their eyes and they'll appreciate your honesty in not trying to sell them something they may not want/need afterall.

Good luck!