In typical fashion, I posted something in a different thread which prompted me to post about a whole other topic in another thread. So let's have at it!
Since day one Pokemon Go has featured certain Pokemon with a massively outsized evolution cost relative to other species. Initially, this was limited to Magikarp alone, but it's since expanded to include Wailmer, Swablu, Noibat, Stufful, Wimpod, Larvesta, and Meltan.
For those who don't play, most evolutions in PoGo work on a standard basis: Pokemon which evolve once typically require 50 candies to evolve (occasionally with an additional item or quest thrown in, such as the Metal Coat for Onix or walking 10km for Bonsly). Pokemon which evolve twice typically require 25 candies for their first evolution, and then 100 for the second (again sometimes with the aid of an item, such as the King's Rock for Politoed or the Dragon Scale for Kingdra).
Some exceptions do exist: weaker, more common Pokemon such as Ledyba have a reduced cost of 25 candy to evolve, while Pidgey, Caterpie, and Weedle similarly only need 12 candy for their first evolution and 50 for their second. Azurill only requires 25 candy for both its evolutions. Several two-stage Pokemon like Accelgor and Ambipom do need 100 candy instead of 50 to evolve.
So looking at the 400-candy crew, it's evident enough why most of them have this requirement:
- Magikarp, Wimpod, and Larvesta all reflect the extra effort needed to evolve them in the main series
- Wailmer feels like a slight meme pick, but it's a nod to Wailord being the largest Pokemon in the series
- It's generally accepted that Swablu and Noibat being part of this group reflects Niantic's general efforts to make Dragon the most elusive type, as well as Noibat's incredibly high evolution level in the main series. Each of the eighteen types has a catching medal that slightly increases the catch rate for Pokemon of that type when certain numerical milestones are hit (for which obtaining Pokemon by trade and evolution both count towards the overall total); due to Dragon being the rarest type, the platinum Dragon medal is fittingly frequently the hardest to obtain. Swablu is weak and relatively common (now - like most things, it was rare when introduced) so the high evolution cost prevents players from evolving a bunch of them to artificially inflate their numbers.
- Lastly, Meltan is a mythical Pokemon, so has a high cost to reflect this fact
Unreleased Pokemon with the 400-candy requirement are Applin (for both evolutions) and Kubfu: these fit for the same reasons covered already. Poipole and Type:Null also both have an evolution requirement of 200 candies. Obviously all of these are subject to change before release.
The odd one out in this group is... Stufful. Bewear isn't a particularly brilliant Pokemon in Pokemon Go or the main series, nor does it have a particularly onerous evolution requirement. It's particularly odd since it literally debuted during a community day with double candy, meaning that evolving it was trivial if you caught a relatively small amount (using Leppa Berries, it's 12 candy per catch), and it has been fairly common since then.
Weirdly, there's an omission here, too: Skrelp. Interestingly, when Skrelp was first datamined, it was a 400-candy evolution. Why? Because it, like Swablu, evolves into a Dragon-type. Skrelp hasn't been a vastly common Pokemon since its debut (shame, because it's a favourite of mine - though coincidentally the shiny will be available from tomorrow) but it's common enough that you could conceivably catch enough to evolve a bunch of them. It was tweaked to have the standard 50-candy evolution prior to release.