Let me tell you, by way of an example, a little about what ADHD costs - even when you have a good income and can mitigate some of the consequences.
My daughter and I are on a trip to Munich, our former hometown, to celebrate her 16th birthday.
We're lucky, actually. There is a direct train which takes 3 hours from the city where we live in Switzerland, and if we reserve enough in advance, it's pretty affordable.
Which I did.