I did a quick scrub of all the lists in the CoK 2023 and identified the top 5 most expensive units in each of the main categories. Here are some quick results!
Infantry
- Nightstalkers: Blood Worms, Size: L, Pts: 290, Sp: 5, Me: 4, Ra: –, De: 4, At: 40, Nerve: 25/28
 - Sylvan Kin: Forest Guard, Size: H, Pts: 270, Sp: 6, Me: 3, Ra: –, De: 4, At: 25, Nerve: 22/24
 - Dwarfs: Ironwatch Rifles, Size: H, Pts: 265, Sp: 4, Me: 4, Ra: 5, De: 4, At: 20, Nerve: 21/23
 - Elves: Palace Guard, Size: H, Pts: 265, Sp: 6, Me: 3, Ra: –, De: 4, At: 25, Nerve: 22/24
 - Free Dwarfs: Free Dwarf Ironwatch Rifles, Size: H, Pts: 265, Sp: 4, Me: 4, Ra: 5, De: 4, At: 20, Nerve: 21/23
 
Cavalry
- Basileans: Paladin Knights, Size: H, Pts: 350, Sp: 8, Me: 3, Ra: –, De: 5, At: 32, Nerve: 22/24
 - The Order of the Brothermark: Paladin Knights, Size: H, Pts: 350, Sp: 8, Me: 3, Ra: –, De: 5, At: 32, Nerve: 22/24
 - The Order of the Green Lady: Order of the Brotherhood, Size: H, Pts: 330, Sp: 8, Me: 3, Ra: –, De: 5, At: 32, Nerve: 22/24
 - Kingdoms of Men: Knights, Size: H, Pts: 325, Sp: 8, Me: 3, Ra: –, De: 5, At: 32, Nerve: 21/23
 - League of Rhordia: Knights, Size: H, Pts: 325, Sp: 8, Me: 3, Ra: –, De: 5, At: 32, Nerve: 21/23
 
Large Infantry
- Ogres: Warriors, Size: L, Pts: 350, Sp: 6, Me: 3, Ra: –, De: 5, At: 36, Nerve: 22/24
 - Basileans: Elohi, Size: H, Pts: 270, Sp: 10, Me: 3, Ra: –, De: 5, At: 18, Nerve: 0/17
 - Undead: Wights*, Size: H, Pts: 260, Sp: 7, Me: 3, Ra: –, De: 5, At: 18, Nerve: 0/17
 - The Herd: Lycans, Size: H, Pts: 255, Sp: 9, Me: 3, Ra: –, De: 4, At: 18, Nerve: 15/17
 - Undead: Werewolves, Size: H, Pts: 255, Sp: 9, Me: 3, Ra: –, De: 5, At: 18, Nerve: 15/17
 
Chariot
- Ogres: Warrior Chariots, Size: L, Pts: 310, Sp: 8, Me: 3, Ra: –, De: 5, At: 25, Nerve: 20/22
 - Orcs: Fight Wagons*, Size: L, Pts: 285, Sp: 7, Me: 3, Ra: –, De: 5, At: 30, Nerve: 0/20
 - Riftforged Orcs: Fight Wagons, Size: L, Pts: 285, Sp: 7, Me: 3, Ra: –, De: 5, At: 30, Nerve: 0/20
 - Orcs: Gore Chariots, Size: L, Pts: 275, Sp: 8, Me: 3, Ra: –, De: 5, At: 20, Nerve: 19/21
 - Ogres: Warrior Chariots, Size: H, Pts: 270, Sp: 8, Me: 3, Ra: –, De: 5, At: 20, Nerve: 17/19
 
Heavy Infantry
- Orcs: Ax, Size: L, Pts: 310, Sp: 5, Me: 4, Ra: –, De: 5, At: 30, Nerve: 26/28
 - Salamanders: Salamander Ceremonial Guard, Size: H, Pts: 265, Sp: 5, Me: 4, Ra: –, De: 5, At: 30, Nerve: 21/23
 - Orcs: Longax, Size: H, Pts: 255, Sp: 5, Me: 4, Ra: –, De: 5, At: 30, Nerve: 20/22
 - Orcs: Greatax, Size: H, Pts: 250, Sp: 5, Me: 3, Ra: –, De: 4, At: 25, Nerve: 21/23
 - Riftforged Orcs: Riftforged Legionaries, Size: H, Pts: 250, Sp: 5, Me: 3, Ra: –, De: 5, At: 25, Nerve: 21/23
 
Swarm
- Forces of the Abyss: Tortured Souls, Size: H, Pts: 200, Sp: 8, Me: 4, Ra: –, De: 4, At: 18, Nerve: 0/17
 - Elves: Drakon Hatchling Pack*, Size: H, Pts: 195, Sp: 7, Me: 4, Ra: –, De: 3, At: 24, Nerve: 14/16
 - Ratkin: Vermintide*, Size: H, Pts: 195, Sp: 6, Me: 5, Ra: –, De: 3, At: 36, Nerve: 19/21
 - Empire of Dust: Scavengers*, Size: H, Pts: 150, Sp: 10, Me: 5, Ra: –, De: 4, At: 18, Nerve: 14/16
 - Nightstalkers: Needle-fangs*, Size: H, Pts: 135, Sp: 7, Me: 5, Ra: –, De: 2, At: 24, Nerve: 12/14