I think everyone is making assumptions that aren't necessarily true.
Assumption #1 - One needs a command dial for every minimum sized configuration owned. In other words, if the core box comes with 4 trays of Reanimates and they can be fielded as 2 trays, one would need two command dials. I don't think this is a reasonable assumption as I don't think we'll end up actually wanting to field multiple minimum sized units in this game. The way I understand the rules, multiple small units will be extremely susceptible to damage and removal. Larger units are just more durable, so it's reasonable to assume you'll more often be fielding larger configurations.
Assumption #2 - One needs the maximum number of trays for any given unit's largest configuration. Again, I think this is untrue. In practice, you'll be bulking units out with the command tray or a Siege Golem, etc. I doubt we'll see too many games where a legitimate block of 48 Reanimate models (12 trays x 4 per tray) is fielded. It seems that they'd be really easy to flank.
Also, in terms of dollar per model... this is a bad comparison. It's more reasonable to look at dollar per tray. Not all models are created equal. Cavalry take up as much space as 2 Infantry models. Heroes and "Monsters" take up as much space as 4 Infantry models. Trays are the universal comparison point. The core box comes with 16 trays of models for $100. That's $6.25 per tray. The Cav and Reanimate expansions are $25 for 2 trays, or $12.50 per tray. The Command expansions are a flat $25 for 1 tray.
So far, we see that...
- Unit Expansion are 2x as expensive per tray when compared to the core box. The upside is that you get SOME new cards/abilities that aren't included in the core box.
- Command Expansions are 4x as expensive per tray when compared to the core box. The upside is that you get LOTS of new cards/abilities that aren't included in the core box AND new poses/sculpts for your unit.
So, what should you buy? If you're looking to field a full size army while minimizing dollar expense, stick with core sets. If you're willing to spend more money to get a more flexible army with a variety of options, look into the expansions.
My intention is to go with a friend, but two core sets and swap out the models. That will leave me with having spent $100 and getting two of all the Waiqar trays. Then, based on my experience playing the game, I'm likely to buy the Command expansion. It really depends on how the game works and how I like the units. If I just love the Archers, I'll buy an Archers expansion. If I hate them, I won't. In these sorts of table top war games, it's not necessarily common to own EVERYTHING an army has to offer. Hobbyists often buy one of everything to assemble and paint, but the hardcore players tend to just buy what they're intending to actively use.