What is objectively the most Cost-Effective unit in the game?

I'm talking the absolute single unit that gets you the most for your resources.

Stat-wise. Situationally it's the Siege Onager or the Trebuchet.

But from a purely on-paper standpoint... Which unit is the most cost effective in the game?

Is it the Slav Halberdier?

The Malay Battle Elephant?

The Goth Champion?

The Mayan Arbalest?

The Malay Two-Handed Swordsman?

The Magyar Huszar?

Persian Crossbow?

The Malay Karambit Warrior?

What unit in the game is the most bang for your buck?

I'm sure someone has done this math already.