So we've gone from the majority of drugs costing a couple of quid and the NHS making "such a high annual profit" to actually the cost of an average prescription being pretty much the same as the prescription charge to those that pay and free or subsidised to a large proportion.
Any money made being a fraction of percent of the NHS medicine budget, let along the NHS budget as a whole.
What's the source for the £140 million profit? I don't think it adds up with the King's fund data.
The key word here is average, the majority of prescriptions are for cheap generics costing a couple of quid, but the minority of really expensive drugs pushes the average up.
https://www.gov.uk/government/publications/dhsc-annual-report-and-accounts-2017-to-2018
This says the revenue from prescription charges is £576 million, which would extrapolate to £598 million for 2018/2019.
The kings funds data differs but even if you use their data and apply it to that figure, the NHS would make roughly a £31 million annual profit from the prescriptions it charges for.
So the point to take away is, with socialised medicine in the form of the NHS, a minority of people that need expensive medications win, whereas the majority lose out.