You’re after all the items to make the Super Cooling Module from Shadowmoon Valley, Nagrand or Talador, and the Cyclical Power Module from Frostfire Ridge, Gorgrond or Spires of Arak. Some are worth only a few hundred but I’ve sold a few for over 20k. They drop from any mob in the zone. I haven’t found an optimal spot, but all these zones have plenty of areas with densly packed mobs.
Always check each of the prices of the item, and look over a spread of several days. This is not so important on small items, but anything that you are spending hundreds of gold on you need to check prices carefully. It is also a good idea to check a website such as Allakhazam, Goblin Workshop, Wowhead or WoWuction to see what an item normally sells for.
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In BfA you can also craft weapons, including Bows. While I don’t have any personal experience I expect the item level 300/310 gear will sell as well as it does for blacksmithing. You can also utilize the level 110 bracers in the scrapper to generate expulsom. This may be cheaper than linen on some realms, but it heavily depends on Blood-stained bone prices.
It's hard to step out of the shadow of Legion, which was utterly fantastic in almost every way, to enter an expansion where you get one item per boss in the last expansion because the rules have been changed to force more grinding, where you have to grind reputation in the old expansion that you probably skipped because rep grinds suck JUST to unlock allied races (who aren't fully unique races since they recycle old content such as animations), where questing has SOMEHOW become boring again and where your new abilities are given by items you'll swap out every level, meanwhile being only boring passive effects no one cares about.