We are a little removed from the Korthite collapse now, and things are normalizing. The silver lining of the high end legendary collapse is that other markets are now a much better way to spend your time relatively speaking.
Opportunity cost
Due to opportunity cost considerations the only market that was actually worth my time for most of 9.1 has been legendaries. With the high prices and strong sale rate nothing was even remotely as profitable as just doing another cancel scan for rank 5 and 6 legendaries. Now that the price has collapsed this is no longer the case. I can now justify doing other things in stead, which is great news as I love variety! So what can we do?
Crafter’s mark gear is moving
With 9.1.5 on the not too distant horizon and bringing in a lot of QoL changes many players are getting their alts ready for covenant galore. Catch up gear is also very strong in general for goldmaking purposes. I started crafting Crafter’s mark of the Chained Isle gear again this week and I got immediate sales. The market is great as you do not have to babysit your auctions, just post and forget, come back 24 hours later to some good sales. Competition might increase as more players look for other markets with legendaries slowing down though. Crafter’s mark 3 will also likely work, but personally I can sell enough chained isle gear that I don’t bother with mark 3 gear at all.
Cosmetics
With 9.1 entering it’s more mature stages cosmetic items should see a general increase in sale rate. At this point in the patch players start setting their sights on other goals with their PvE or PvP goals mostly done. This leads to more gold being dropped on cosmetics as players don’t need to or want to spend as much gold gearing and keeping their character up to date. There are tons of opportunities here, my personal favorite is crafted mounts. All of the various engineering mounts, JC panthers, Vial of The Sands etc. You can also do battle pet flipping or old world crafted transmog. Battle pets will take a while to get going, but crafted transmog is fine, just start with any profession you have and craft anything with a big enough green number.
What else?
There’s always going to be other opportunities as well. All the other SL professions can craft useful things, anything from missives to transmog will still sell. They are currently not quite on the level of the gear crafting however, so if you can, prioritize that. There’s also a literal ton of old expansion cosmetics to delve into so let your imagination run wild. If it looks cool, someone will probably be willing to pay for it!
Good luck finding new markets!