You don't need to sell high LV mats to make money either, sell cotton/flax/shards/etc.

People who want to power thru levels will buy them, even I do when I cbf to gather my own stuff. HQ mats sell quickly especially if you aren't price gouging. Don't expect a huge flow of Gil all at once, but an hour of harvesting can net you 10,000+ Gil if you do some research before spamming things into your retainer.