See, now, the difference is that you can kill Coteaz.
Fair price for Coteaz, honestly? Maybe about 150 pts, same as a Librarian. He's got some neat little extra abilities over a libby, but they don't get used that much, and he's T3 and no invo save. I'm careful with him, but he gets doubled out by plasma or random str 6 weaponry surprisingly often. The ability to take Henchmen is key to a lot of people, but personally I don't really love henchmen troops and rarely use him for that.
I've been honestly looking to switch him out for a libby but the spare 50 pts is hard to come by. But yeah, fair price for him is about 150.
Celestine? Consider that she costs the same as Anval Thawn(40 base for the termie, and 75 for the upgrade), who has the same ability but is otherwise just a mook. He's probably about the right cost, or maybe just tad too expensive--I often think of taking him but don't. But Celestine is highly mobile and a combat beast, she can cross the board easily and will on average kill about half a tac squad. She often denies you Slay the Warlord and can easily contest objectives. There is absolutely nothing smart you can do against her...try to tie her up with something tough that will have trouble killing her, like a Dakka-dread? Lame, and good luck catching her, anyway.
Appropriate cost is something north of 200....225? She's doesn't have the punch of Mephiston, but the unkillable thing is a pretty huge deal. Really, I don't think something like her should exist. The fact she's completely unkillable removes tactical sophistication and makes the opponent feel helpless.
