EPTI'm aware of a couple flaws in the following, however they are merely numerical in what aims to be more of a theoretical paper. Enjoy.
The True Cost of A Unit
In the RTS Genre, there are many things to consider. You have to manage your resource gathering, your unit production, the various skirmishes around the map, teching, and whatever else may be thrown your way.
One of the staples of the RTS genre is the cost vs. value of various units. Of course, unfortunately in StarCraft & StarCraft II, the value is constantly shifting depending on the situtation. When faced with Colossi, a squad of marines will be almost worthless, however, when approaching Stalkers, Marines are an invaluable counter. Thus, in a situation where your opponent has massed Stalkers vs. the situation where Colossi are the main opponent, the value of the marine changes.
Traditionally, each unit has a base cost, and this is a static number that can be regurgitated from each and every StarCraft veteran. You say, what is the cost of a marine? Most will say 50 minerals, 0 gas. A keener might even say 50
minerals, 0 gas, and 1 supply.
However, both of these lack the true cost of the unit. For this post, I'll be explaining everything to consider in the cost of a unit, using the bread & butter Terran unit, the Marine, as an example.
To build each unit, you require a certain number of structures & tech. For this example, the Marine requires very little in the ways of tech - solely a Barrack. Thus, Marines cost 150 minerals to even begin production.
As well, you must consider that to construct a Barrack requires time: Possibly the most valuable resource in an RTS as it is, of course, real-time.
To build a Barrack requires 60 precious seconds. Once it is complete, you can begin the production of Marines. Thus, before we've even begun Marine production, we have spent:
150 Minerals
60 Seconds
Now you want to build your first Marine! Fair enough. 50 minerals and 25 seconds later, out comes your very own Tychus Finley ready to wreak havoc on all your opponents!
But wait! There's something else to consider. We mentioned that a Marine costs 1 supply. That must present some additional costs, doesn't it?
Of course it does. A Supply Depot comes in at a sly 100 minerals -- an easily forgotten cost. And it racks in 8 supply power, giving you the potential for 8 more bloodthirsty killing machines.
Right on! But this adds even more to the cost of our Marines! 100 / 8 is 12.5, thus each Marine actually costs 62.5 Minerals to produce.
But wait, we're forgetting about a crucial feature! The Reactor is a new thing in StarCraft II, and helps immensely in Marine production. For a small price of 50 minerals and 50 gas, you can have two production queues pumping Marines simultaneously. Of course, since regular Marines require no gas -- the Reactor brings in the extra 75 minerals of pre-cost, as it requires a Refinery to have been built prior to it's construction.
Building a Reactor also requires time when no Marines are being made to construct itself. In fact, it takes 50 seconds.
So, your pre-build cost has already begun to mount:
225 Minerals
50 Gas
110 Seconds
That's even before you've begun a single Marine! Jeez. Is the Reactor even worth it? Well, you consider it requires an extra 50 seconds to produce, and after the fact your production queue is doubled. So let's take a look at the math behind this -- starting at Barrack completion.
25 seconds after Barrack production -- the Reactorless Barrack has produced 1 marine. The Reactor is still building, thus the Reactored Barrack has produced zero marines; edge: Reactorless Barrack.
50 seconds after Barrack production -- the Reactorless Barrack has produced 2 marines, now. The Reactor just finishes building, and has yet to produce a single Marine; edge: Reactorless Barrack.
75 seconds after Barrack production -- the Reactorless Barrack has produced 3 marines, now. The Reactored Barrack finishes it's first two Marines, but falls short of the other; edge: Reactorless Barrack.
100 seconds after Barrack production -- the Reactorless Barrack has produced 4 marines, now. The Reactored Barrack finishes it's second two Marines, balacing out th two; edge: Tie.
And at all points after the 100 second mark, the Reactored Barrack will produce twice as many units as the non-Reactored. Thus, for the Reactor to be truly valuable, it requires 100+ seconds to come into fruition.
That could possibly be critical time in the defense of a quick Zergling rush.
So, now we have considered most of the cost of a Marine. But what of the value?
Let's take a look at a few examples:
In a bunker, the Marines are fortified with an extra 400 collective hit points for a cheap 100 minerals @ 40 seconds build time. This provides a static place where each marine could be said to obtain a bonus of 100 hit points (although this is not entirely true due to the nature of the focus fire, however in theory it makes the concept simpler), giving it a total 145 hit points. With 4x6 damage, as well (this accounting for no upgrades being performed as they add cost that is getting pedantic to calculate) So this is like a large, static marine with 580HP, doing 24 damage per shot (with a small cool-down in comparison to most units, in fact: the missile turret fires at the same speed of the Marine, and the Auto-Turret is only marginally faster). Thus, you can see the value against Zerglings and/or Banelings, with only 35 hit points. The additional 5 range verses the melee range gives them plenty of time to shoot one or two down before the battle even begins, and then the 580 (theoretical) hit points and 24 continual damage can end a fight quite nastily in your favor. Of course, there are additional things to consider, such as run-bys that leave your static Marines to require
pulling-out and moving, severely lowering their hit points while maintaining their effective firepower.
However, marines in a bunker are extremely vulnerable to, say, Hydralisks with the Range upgrade. This puts their range at 6, leaving them to win uncontested in a flat-ground brawl.
A good example of the power of a bunker to even a fight is 4 Marines in Bunker vs. Roaches.
Roaches have a miniscule range (3) and a long cool-down (2.0) versus a Marine's range (5) and cool-down (0.86)
This means that a Marine can fire thrice in a little longer than a Roach fires once. So, four Marines firing three times does 72 damage, and a roach firing once does 16. This means in two cycles, a Roach takes 144 damage and the Bunker takes 32 (approximate) and as Roaches have 145 Hit Points, they will die after approximately two "rounds" of combat (the extra damage will occur during the Range gap of 5 to 3). Thus, four Marines in a Bunker vs. four Roaches is a rough win for the Marines: Because, after two rounds of combat, the first Roach is killed -- reducing the Roach team's effective combat damage per round from 64 to 48. In these first two rounds, the bunker incurs 128 damage. One roach dies. After two more rounds, the second roach dies -- and the bunker incurs an additional 96 damage, bringing the total to 224. In two more rounds, the third Roach dies -- and the Bunker takes 64 additional damage. The total damage is 288. After the final two rounds, the bunker takes it's final 32 damage, and the fourth roach dies -- the bunker standing tall with 80 remaining hit points. And, considering that the Marines are relatively cheap compared to Roaches (which on top of their 75/25 & 2 population [25 extra minerals for supply] + 200 Spawning Pool + 150 Roach Warren, and 65+55 seconds for the construction) the fight made even with a simple 100 mineral bunker makes this knowledge invaluable. Right on, right? Plus, SCVs can repair bunkers while the fight goes on, and increase the combat effectiveness of the squad as a whole.
I haven't even touched on Stimpaks and Combat Shields, and already the Marine seems a little deeper already.
Thanks for bearing with me as I ramble, and I hope you took something from this, and understand a little better the true cost and value of a unit, and can start exploring (maybe not as indepth or maybe more-so than I have here) your own possibilities that lie within StarCraft II: Wings of Liberty.
~SassySally
Look forward to some more!
