I can only speak for myself.
I manufacture T2 modules which I sell.
I do this, in general, by buying the inputs I need and selling the finished product.
I look at the supply chain, and if there is a substantial saving/value add in my making one of those components then I will. On a case by case basis. The default view when going into a new product line is “can I just buy-make-sell at a profit?”.
I have a real world background in a lot of this.
I make an adequate profit (billions of ISK per month) on a scale where I can disrupt my local market in Amarr. I try not to as I’d rather milk the cow all year than just have steak tonight.
Right, that’s the background.
An industrial operations, run by an “industrialist”, doesn’t have to do everything from raw materials to finished product. Eve is a rare game compared to others that have “crafting”. Eve is very complex and allows supply chains to emerge. Eve is a very good business simulator because of that.
This complexity is deliberate - it causes interaction between players. CCP have driven changes that way.
I think this is a good thing by the way.
You rarely see in the real world a fully integrated rock to consumer product business. Rio Tinto produce refined materials. Walmart/Tesco buy (and may brand) completed goods, contract with a hauler to ship them to retail.
There’s a company that specialises in making tin cans but don’t mine tin, but they don’t make baked beans.
Ford doesn’t make the electronics that go in their cars. Heck, Ford sometimes aren’t even making the car they sell.
What they do is focus on being good at their bit and getting supplied by others in the marketplace that are good at doing their bit. Either just by purchase of by buying with a long term strategic relationship.
Sometimes you may look at your supply chain and go “there’s a real profit in there and I could do that step” - but you do that while being aware of the opportunity costs, and the risks of doing it.
For example in Eve: I make Inertial Stabiliser IIs. Not a huge profit, but a nice little reliable earner if you don’t swamp the market. They need a bunch of components, one of which is the Inertial Stabiliser I, which is made from asteroid materials.
I could make a profit buying the materials, making the T1 part and selling it on the market (where I buy it). I could thus make more profit (rather than giving it to my T1 supplier through the market) by making the T1 I need but i don’t. because it takes time and (importantly) manufacturing capacity I can more profitably use for T2 work.
This is Opportunity Cost.
Fun as mining is, it takes me away from making a profit.
Ask yourself, deep in you heart “why am I making this…?”
Read “Wealth of Nations”.
If you want to make a something from complete scratch - good on you, everyone needs a hobby (and this is a game - so that is a fine thing to do). But be aware that you could be making a better income by thinking of what your business actually does to make a profit.
Assuming of course you are wanting to make a profit.