You don't even need really high crafting skill to be honest. I found that I could game the crafting system with a very poor crafting skill.
Uncommon-rarity Nekomata rifles were my early key to it. With no perks/upgrades at all, they cost something like 30 common & 20 uncommon components to create. Sure higher skill levels & perks do lower those costs (higher profit margins). Either way - the income from crafting then selling one (nearly 650 eddies) is higher than the cost of purchasing those same components from a junk vendor. By only using an uncommon-rarity recipe, you avoid requiring any of the more scarce components, so it's easy to find plenty of what you need and then purchase any extras.
Later-on, I found a recipe for an outer torso uncommon jacket which nets nearly 850 eddies per sale, for the same crafting cost as the rifle. Now I'm using those instead. If a vendor runs out of components to sell you, I believe skipping time will cause them to restock, plus of course you can do a little "vendor tour" and visit a few places which are in the same vicinity (also useful when you drain a vendor of funds).
I haven't actually gone totally mad on any of this yet (I'm yet to purchase any components from a vendor), because I still have 17,000+ common components spare and 8,000+ uncommon components spare with my V. But - yesterday it took me only 15 min or so to raise 35k eddies via crafting when I wanted to buy a second heart implant to replace my not-worth-it bio monitor.