This also isn't just a thing exclusive to Cosmic Exploration, but crafting/gathering in general.
The more accessible it became the less profitable it was as a result, and the removal of HQ materials basically killed gathering as a money maker.

Back in Stormblood, and even more so in Heavensward, you could make filthy amounts of gil with just crafted HQ combat gear and raid consumables. Prices stayed high simply because, while everyone needed it to raid, only few had the omni-crafter skills and gear to make it.