Thing is, as in real life, opportunity cost is the real key on this. I'm getting 2 tokens per month quite easily with just 3 toons (1 maxed only (yeah, pretty damn inefficient but I lack a lot of time to play :p)) just by flipping couple of things, food, flask, potions, bags, shirts (yeah, shirts!!), etc etc. Every damn penny/gold counts :p, just have to learn how your realm market works, what niches exist, which items are needed and undersupplied and which are oversupplied.
You will get the recipes for these high level armors through a new discovery system. First you have to craft the base ilvl 355 armor (normal raid ilvl) which requires BfA Leatherworking 115. After you craft this armor, you will discover a new recipe, which is ilvl 370 (heroic raid ilvl), and after you craft one from the ilvl 370 armor, you will discover a new recipe for an ilvl 385 armor (mythic raid ilvl).
I think that's server dependant. I make a lot of Golems, but the price on my server is high enough that you could buy all the living steel and still make about 20K (almost 200kg on AH). Its just that you proc all the way up the chain. You proc 20% of your trillium, and then 20% of your living steel. SoH and Ghost Iron are such low effort farms, too. 20% of 180 Trillium Bars at 500g is 18k more profit, 20% of 150 Living Steel at 3500g is another 105kg. That's an extra 25k profit per Golem. If they stop selling stockpile them for the next expansion, they always boom with the price of herbs. And a consistent 20% proc rate is the opposite of RNG, its extra free stuff as a benefit to completing an extra quest (not to mention for new alchemists the investment of leveling Vanilla Alchemy). You're looking for some get rich quick scheme, where the real way to build wealth is patience and volume. No market is going to be viable because you want it to be. Only because you make it viable.