I will write to you how it is done in other games.
First, you need to distinguish between new players crafting for themselves and then crafting for existing players.
The first one is doable, the second one is not. F2P games that have two types of subscribers - alpha/omega clones - like for example Archeage (they have patrons/non-patrons) failed in trying to make possible crafting between them - because patrons could just make non-patron accounts.
Subscription based games tried to make low level players useful for high level players (like Manor system in Lineage 2), but that didn’t work either. The idea was to make the low level gathering as mundane as possible so it was only rewarding for the low level players. The problem was that in a lack of low level players, which occurrs at some point, it made crafting impossible as no high-level player wanted to do it - this happened in Dofus and also in Archeage with basic trade packs.
Crafting for themselves is possible due to game mechanics that rise the price. Like for example traveling costs. Traveling is a money sink in many games and when you want to buy an item you need to calculate also the cost to travel to the auction house.
Usually games have multiple types of crafted items - permanent ones (like equipment) and items with one time use - consumables. The permanent ones are usually done by dedicated players and the equipment crafting is mostly considered as an end-game PVE content - in F2P games it is usually behind a paywall. But consumables are crafted by everybody - potions, food, antidotes, dyes, … The reason is that you need them constantly and is impractical to travel to get them.
In some games crafting has additional uses like for example repairing or enchanting which requires a crafting skill - you can only repair/enchant an item you are able to craft.
Some games have a mastery system - the crafted item (like a sword) knows who crafted it - and if the equipment is used by that person, it gets additional bonuses.
Some games have daily crafting quests. You craft an arbitrary item for which you need to get resources. For example in Aion Online you first need to get the material from an NPC (a distribution mission) somewhere in the region (on lower levels the NPC is closer to your place) or gather it from a specific place (a mining mission) and then craft it. In subscription based games this is usually done to raise your crafting level (as crafting on lower levels and trying to sell the items ends in a loss), in F2P games you usually get points (something like LP) that you can redeem in that specific crafting department shop.
Mostly games use some kind of a leveling system that makes for the lower level items the difference between new crafters and skilled crafters diminishable, meaning on lower levels the difference in crafting costs is minimal. This is also coupled with the gathering system - meaning an experienced gathered and a new gatherer gather the same amount of the low level material (like copper ore) in the same time.
In real life you have empire trade wars (like between USA and China), so you have subsidies and region market protection (custom duties, tolls, trade restrictions). In RL Gallente, Minmatar and especially Amarr wouldn’t just sit there and watch Caldari getting rich on taxes in Jita.
If you want to ask about a specific thing, I can provide you with more details and give you an example how it works.