First of all, the FDA has approved several ketamine-based treatments including the IV drips. They are expensive because, well first you have to lay a drip and second, due to the massive side effects you need medical personnel at hand (which makes it expensive). Recently, a ketamine-based nasal spray has been approved, but you still need medical supervision to use it. So that is rather a bad example for your case.
While blaming the FDA is very popular, it is really not the limiting factor. Just to provide some numbers, trials for FDA approval average to about $19 million. The average cost for developing a new drug is roughly 2-3 $ billion, i.e. FDA approval is just a small fraction of the overall cost. Looking at overall expenditures, marketing takes up about the same amount as research (depending on company and product it can be much more or less), again dwarfing the FDA-related costs. So no, if companies do not develop something it is because it is not financially viable it is certainly not due to the FDA.
Moreover, it still does not limit public research institutes.
Edit, I accidentally crossposted with Strange, but since I feel that my post is addressing a common talking point, I am going to let it stand, unless there are objections.