Why are "spawn units when Hero is knocked out" techs so expensive?

I’m mainly referring to 1 tech (Filiki Eteria | Age of Empires Series Wiki | Fandom) and 1 card (Niños Héroes for Mexico). The first spawns an Evzone skirmisher (or two, depending on testing) upon your Hero getting downed, and the second spawns a single Militiaman upon your Hero getting downed. Filiki Eteria is an 800c tech unlocked from the native Phanar Athos Monasteries so it’s locked behind 2 separate payments and is very expensive, while Niños Héroes is a whole age 3 card.

Does anyone use these things? An extra couple of Evzones or Militiaman in a large battle or two isn’t going to have nearly the impact that 800c or an age 3 shipment will have, ever. They’ll never pay off. The only thing I can think of would be something like a cheese with native civs bringing their War Chiefs back really fast and throwing them at large camps of treasure guardians to get infinite Evzones, but something tells me that wouldn’t work.

Clearly the devs think these effects are very strong. Filiki Eteria was buffed from 1000c cost to 800c at some point, and Niños Héroes has been in the game for a very long time untouched by patches. What am I missing?

I personally think the hero card for the european is more of a trap of flavour theme card, the ninos card and this tech is also fall in that category.

The idea that when a unit died it spawn a weaker unit is a nice concept, but applying it on hero is just too limiting. Different story for the Mexican card Catrachos from Central American revolt.

You can harass workers pretty efficiently with it.

And same goes for the Chichimeca Rebellion card for the Aztecs.

The tech from the monasteries is kinda nice in treaty, and I’ll actually use the monasteries in sup for the coin improvement for the two mines, the healing, and the XP tech (meaning even without that one tech being used, the monasteries at least see occasional use).

The card version for Mexico could honestly be removed. I do kinda wonder if they kept it in mostly because they wanted to do something with that mechanic at some point and they figured out how to make it work (I don’t know how hard that is to code).

I’d leave the monastery tech as is (or maybe 600c?) and move the Mexican card to age 1 probably.

they are pretty good for specific strats like Baja or using Berber/Akan Heroes or getting the cards for extra explorer/general as Ports/Mexico.
That would also be the best way to use the Phanar tech by getting two buffed explorers as Ports without a cooldown to buy them back and just have them tank at the front with 1k+ HP or even more in age5 and spawning an evzone for 200c each time.