This is true.
However, if you start your session with 1 million ISK, mine 1 million ISK worth of ore, refine it to 1.2 ISK worth of materials, and just sell the materials, you have profited by 1.2 million ISK. Your profit is objectively higher by not falling for the “my minerals are free” trap and just maximizing how much you refine them for its own sake.
Instead of thinking of it as profit, think of it as creating or destroying value.
By refining the ore into minerals, you have created .2 million ISK of value, so you should very clearly do this.
However, by producing a 1.1 million ISK set of goods with 1.2 million ISK of materials, you have destroyed .1 ISK worth of value. Thus, you very clearly should not do this, barring extenuating circumstances like a slow mineral market (unlikely) or hauling concerns (both in terms of getting minerals to market or getting what you buy at market to where you are).
It is perhaps misleading to say that minerals you mine aren’t free. However it is important to understand the sentiment behind that idea: The minerals, ore, and goods you produce all have a set value at every stage, and it is a very common situation for value to be destroyed if you refine your daily loot (Ore, Minerals, Goods) too far.
It also is important to remember that even if making minerals into goods is a good deal, that by mining you aren’t earning ISK some other way actively. Mining 1 million ISK worth of ore that you refine into 1.2 mil of minerals that you build into goods worth 2 million ISK is strictly inferior to running missions for say… 20 million ISK, and then buying the minerals for 1.2 ISK to convert into 2 million ISK goods.
Again, we can look at value created a session. The miner created 2 million of value in their session by refining their entire haul, but a missioner could create 33 million in the same time, because they could make 16 times as many goods with bought minerals than the amount of minerals the miner could mine in this hypothetical scenario, just by not falling for the psychological trap of assuming that buying refined materials is worse than making them yourself. At the end of the day, everything has an ISK value, think of all your assets as pure ISK. It is best to think of it like you HAVE to refine ore directly into ISK, but can do it at two different rates, the reprocessing rate (AKA the value of the minerals you make) and the market rate (the value of the ore sold). Likewise any industrial activity is just refining minerals into goods to sell for ISK, compared to the market “refining” minerals into ISK. Find the method of refining that has a better rate.
Or, to put it another way, if you had two buttons on the refine pannel, and one said it would increase the value of your ore by converting it into 1.2 mil of minerals, and one said it would reduce your ore’s value by converting it into 1.1 mil of minerals, it is VERY clear which one you should pick. Until and unless a situation (like the hauling issue Bjorn has) makes it so that refining and selling are not essentially equivalent at whatever stage of refining you are on, you should always pick whichever one gives you more ISK worth of assets. In your hypothetical case, you should refine ore into minerals via processing, and then refine minerals into ISK via the market, rather than refine minerals into goods, because the market is giving you a 100% reprocessing rate, and manufacturing is giving you a 91% reprocessing rate.
You have to be rather unusual (Like Bjorn, who has multiple circumstances that make mining clearly the best solution for their needs, because they both can’t the level of PVE content that surpass mining in ISK, and because their location makes hauling to transform the minerals into ISK into ) to make solo mining the best way to handle yourself.
