Plus your math is completely wrong: the upkeep from marines + a ship is much less than what you make from a few raids. Just a simple pirate station will give 20k+ in supplies and fuel and small/medium core planets give similar or more. None require very much investment (I think for pirate bases I break even if I hit 1 every 6 months, and that's with taking no marine bar missions at all. Those pay good money: a single one of those will cover a years worth of marine expenses, easy). Only the major military worlds have all that high defenses.
Actual cost:
Approaching: Hostility for going in loud, OP/Story point for Insulated Engine Assembly and Militarized Subsystem and One Whole Skill Point for Sensors if stealthing. A few phase ship are useful so maybe One More Whole Skill Point for Phase Coil Tuning if you are going that route.
Crack the Orbital station:
Supplies and fuel cost and weapon cost of a fleet that is able to take on a station (because you amass this naturally), Deployment cost for ship you deploy to defeat the Orbital station and its defender, Recovery cost if your ship go boom, Hostility/Relationship cost for the act of piracy
Tactical bombardment: Fuel cost depending on target's ground defenses.
Ground support ship: Time cost/Credit cost you need to find and obtain the Ground support ship, Recovery Supplies cost if you decide to steal the ship, Supplies and fuel cost when you lug your Ground support ship to the target, storage cost when for some reason you store your ship outside an abandoned station, Ship slot cost for lugging around ship unsuitable for combat
Tactical Drill: One Whole Skill Point. Opportunity cost of using that skill point elsewhere.
Marine: Credit cost for buying them, Credit cost for their salary, crew space.
Raiding: Credit cost and time cost to replenish lost Marine, (Possibly) Story point cost if you decide to use it, Hostility/Relationship cost for the act of piracy.
Inventory: Storage space for the extra cargo to hold the loot, Supplies and fuel cost for the extra cargo ship.
Destabilize and decivilize: Raiding reduce stability so you can't keep doing it.
Some of it is one time cost, some you continue to pay, I see that as "require very much investment". I also see you are ignoring quite a bit of the necessary calculation.
Considering you can skip majority of that by attacking convoy, getting a lot more loot without having to deal with a station.
I reassert my claim that raiding are no where near profitable enough. Achieving less, with more.
Using Heavy armament as example, Raiding usually never give you more than two digit, but attacking convoy or even invasion force can give you 400 or so.
I can even argue that invasion force are the best target as they give you ton of Heavy armament, Supplies, Metal and weapon.
This explains it: You are playing with mods that completely change how raiding and ground combat works. The base game is not like that.
That doesn't explain anything. I don't really know what make you think that.
I mean if you have overwhelming force to easily raid, you are more than likely to be able to take over a colony by force.
Taking a colony is good because colony generate passive profit , dismantling colony are instant profit.
It is just a simple statement.