> are there doors that an ADHD diagnosis opens that have a better ROI than, say, graymarket modafinil?

I suppose it depends where you live.

Here is what I can think of off the top of my head:

1. Potential legal protections and academic/workplace accommodations if necessary (US has ADA as an example).

2. Access to potentially more medications (modafinil is not commonly prescribed in the US for ADHD -- even off label)

3. Perhaps less trouble than having to use the Graymarket? Less risk of getting caught? I'm kind of grasping for straws at this moment.

If what you have works, then I guess keep going? Just please be careful. Unregulated areas of markets, healthcare, etc. make me nervous, personally.