I got my ADHD diagnosis privately (mostly because of the length of the NHS waiting lists, and I'm currently waiting on a NHS RTC provider to transfer my care there) and I pay the trade price plus pharmacy markup (so ~£40/mo) for my medication, for whatever it's worth as comparison.
Definitely not cheap (I would prefer the £9.90 NHS prescription fee) but I get the feeling that it's cheaper than I would pay elsewhere in the world anyway.