I think there is some confusion here - probably my fault. I put the dacian elite skirmishers up against triarii in a custom battle, I did not put spartan hoplites up against triarii. I'm sure spartan hoplites would crush triarii. They'd do it cost in-effectively, mind you, but I imagine they'd do it.

The result for the dacian elite skirmishers was actually much worse, because I only used a single unit of triarii against them. In truth, I should have used 2-3 units of triarii. This means the dacian elites are total crap, because of their cost.

If you have the money, why not just recruit them? Nevermind the logic behind it. That's just part of the fun.
No. If I am intended to recruit them, then the numbers should reflect that. As it is, the numbers say DON'T recruit them, so I don't and won't.

It's not fun for me to recruit grossly cost-ineffective, sucky stuff - in other words, to hurt myself. I don't walk around during the day hitting myself in the head with a hammer every 5 minutes either.

Most players are just fine with the current system. Also, did you notice that Spartans have unusually high stamina and higher morale than Triarii?
Again, talking the elite skirmishers, not the spartans. But spartans are way, way overpriced too. And I don't give a crap about their higher morale - my units almost never break, not even entire armies of strictly levies. Or, if I have one break here or there, it doesn't really affect the outcome. I rarely enter into battles I can't or won't win.

Even if morale for my troops was a problem (it never is), I doubt the higher morale of the spartan hoplites justifies their grotestquely higher cost. 10 units of the lower end, lower moral stuff that breaks easier would still beat 1 unit of the spartan hoplites that never breaks.

The more elite units have such high upkeeps because in reality there weren't many of them around, as you cannot restrict how many and how often you can recruit units in RTW giving them a huge upkeep to encourage the player and AI to stick to realistic numbers was the best option available.
It wasn't the best option available. In fact, turning what should be great units into utterly crappy units by making them so cost-ineffective is inexcusable. INEXCUSABLE.

If they wanted to force players not to build too many of these elites (perhaps a dubious proposition in itself, but I'm not here to debate that), the best options would have been some combination of 1) taking multiple turns to recruit the units, 2) severely restricting the recruiting area for the units, or 3) severely shrinking the unit sizes of the units. See, that took me all of 10 seconds, and I came up with 3 alternatives that are better than what they chose to do - make the units so grotesquely expensive that they SUCK. Make no mistake, a unit will always suck if it costs too much, irrespective of whatever fantastic stats it may have.

It's fun as it forces you to rely more on regular troops and not spam the whole map with elites, which is just lame, silly and overly a-historic.
Maybe it's fun for you, but it's not fun for me because I simply am not allowed to build the cool units, and thus I have to play the entire game with cost-effective levy spears.

The designers of this mod had many skills and talents - many. They had imagination, they had historical knowledge, they had map-making skills and modeling skills, even musical skills. One thing they severely lacked was skill with balancing and numbers.