Mines

There are four aspects to Mines:
 * How much raw damage it dishes out.
 * How well it breaks enemy morale.
 * How good it is disrupting the enemy.
 * How cheap it is.

Raw Damage
For context know that an unupgraded Tactical Space Marine has 300 HP and that a Dreadnought has 2300 HP.
 * Mines do approximately 50 damage to all armour types except vehicles.
 * Against vehicles mines do 150 damage.


 * Mines deal area of effect damage.

Vehicles can be taken down by mines
Don't underestimate them. Mines can 'explode' eight times, and they can do so every four seconds.
 * A dreadnought that stood on a Mine as it killed a Listening Post would take 1200 damage.
 * Two mines would mess up a dreadnought.

Mines do friendly fire damage, ouch!
Mines deal friendly fire damage (both morale and normal damage). So it is more beneficial to draw enemies into mines rather than flee across minefields, though that can still be worth it.

Mass
Mass measures a unit's resistance to displacement, such as from artillery or mines.

Mass does not scale via upgrades
Mines are just as effective in the early game as in the late game in terms of displacing the enemy.

Later tier units often have higher mass
Units with higher mass soft counter disruption tactics.

Those units with both high mass and no set up times hard counter disruption tactics. A great example of this is Obliterators.

The average mass of a unit varies by race
Certain races naturally have lower mass than others, for example Dark Eldar.

Further, melee armies find it more difficult to deal with mines than ranged armies. Thus your consideration for mines should vary by matchup and unit composition.

Force
This measures the how well a weapon, ability or special attack can displace an enemy.

Morale Damage
Mines also do significant morale damage, making them valuable against Daemons.

Most researches do not scale up maximum morale
As the highly popular general HP and Damage upgrades do not scale morale, mines could still be just as effective later on for morale damage.

AOE Morale damage is better against larger squads
As morale generally does not increase as you increase the size of a squad, mines are far more effective against larger squads than smaller squads.

Commanders are affected by mines to varying degrees
Certain races have commanders that can purchase wargear that significantly increase their mass, for example the Force Commander. Other races' commander, such as the Eldar Farseer, are significantly disrupted by mines.

Countering Mines
Other than units with high mass, as stated previously, there are other ways to counter or mitigate mines.

As the damage is more or less evenly distributed across the squad, healing significantly reduces their effectiveness.

Over time it gets easier to mitigate mines

 * Keen Sight (which detects invisible mines) is more available.
 * Gunlines are more prevalent, so you can destroy mines at range.
 * The raw damage of mines is less relevant, as units scale in HP.

However, the value of mines increases over time

 * The more expensive the model that gets disrupted, the more valuable the mine.
 * The prevalence of special weapons in the later stages of the game makes mines drives up the cost of each squad. It also drives down the HP for Cost of the squad.

What are the factors of production for mines?
The maximum number of mines you can have is 4, which is regardless of Tier.

Mines reduce in cost as you progress through the tiers.

Mines take 30 seconds to build. Thus it is worth delaying the oncoming enemy force in order to get out a few mines.

Mines initially cost 50/35, which is roughly half of the cost of most researches.