hi, builder.
this job sounds like one of those unusual ones that you can't price normally without looking at it.
cost of plaster on the ceiling will depend on what is already up there, what kind of superstructure is there/may have to be erected to suspend the ceiling and how fiddly the job is.
cost of 15-20m of tiles can't be worked out on a per m rate because the job is too small, but in effect it is a 2 day job - one hour on day 1 to waterproof the area where tiles will be stuck, one day on day 2 to glue on all the tiles, one hour on day 3 to grout the tiles plus clean up. Most tilers will just give you an all inclusinve quote but the way i described it gives you something to work on, since I (and other tilers I know) will charge you for 2 full days work total at $300ish per day and that's that.
As for the exposed pipes, it's pretty unusual, since that stuff is usually concealed within the wall/suspended ceiling/slab. Sounds to me like something went wrong during the build process and it was an owner builder with low standards or something like that.