^ Finding out levels are great and all, except a Pokémon's level has nothing to do with its IVs. Not sure what you're trying to say comparing Stardust cost with a Pokémon's IV spread, which is what the appraisal feature is supposed to help narrow down.
It can be CP160 with 0/0/0 at level 19 or CP60 at level 5.5 with 10/10/15. So you're saying by looking at the Stardust cost, you can pinpoint all three stats' IVs? Not sure what this is about.
What the appraisal feature does is immediately give you an idea upon capturing or hatching a Pokémon whether or not it's candy fodder or requires a closer look.
For instance, I caught a wild CP904 Exeggcute yesterday. Normally I'd keep every CP600+ Exeggcute (level 20+) I find just because I know the potential for a beast Exeggutor would be right there, but I'd have to deal with finding out individual IVs before evolving.
The appraisal feature immediately tells me that the overall potential the Exeggcute is a
minimum of 82% (37/45). Great. Then it also tells me that both attack and defense IVs are perfect. Splendid. Knowing that, the stamina has to be at least a 7, which I would still take.
All this without doing anything other than reading the text the team leader spits at you. In the end, its IV spread is 15/15/13 or 95.6%.
Should the team leader have said something like "Overall, your Pokémon has certainly caught my attention" and pointed out she's impressed by its stats for one category, then I know the remaining two stats are each less than 13, but must combine to be 17-23. The range is pretty big, so I'm curious whether this Pokémon has a 67% or 80% IV rating so I'll hold onto it for further investigation. Any rating lower upon appraisal, I wouldn't even bother keeping so its an easy way to maintain storage.
Let's forget the appraisal feature is there at all. Can you look at this Vaporeon and immediately tell me what its IV spread is across attack, defense and stamina just from looking at its candy cost, without resorting to powering it up? Let's say candy is valuable and for the sake of evolving a super rare Pokémon for this level 13 player, they don't want to use any.
Mind you, the appraisal feature is by no means perfect. But it's a hell of a lot better than having nothing at all to point you in the right direction when judging the potential of a Pokémon, without resorting to calculators and apps.