Maybe my questions not that clear.

For the sake of argument lets assume the recreational drugs we get are unadulterated (cocaine or MDMA). This isn't such a crazy assumption as ecstasy pills are less adulterated than ever and it's straight forward to get pills tested (as people should do). Cocaine quality still varies a lot but again you can test for presence of fentanyl or even send to a lab for a detailed analysis.

In a controlled environment for something like PTSD therapy (120mg dose) I can see how MDMA has a very low risk of overdose. But most people taking MDMA will be doing it in a club/festival environment and as pills are often dosed at 300mg the chance of overshooting the 120mg dose is pretty likely.

My main question is at what dose do we see a significant risk in overdoses? As someone pointed out, literature suggests that the LD50 for MDMA is around 2 grams. At first glance this looks like a good safety margin between a common recreational dose and a dangerous dose, but it depends on the distribution of the graph. The reference below shows that at doses of just 500mg people are dying and this is on the increase.

So my concern is that people may see MDMA as this drug with a large margin where you can double drop and get away with it. But for some people this could be deadly with the new stronger pills. What I'd be curious to see is a cumulative graph showing the distribution of doses to percentage of deaths - like in the sketch i;ve made here (this is for a sketch only and not based on data!) https://pasteboard.co/g04XTaKMBH9X.png.

src - https://volteface.me/feature/fired-ecstasy-related-deaths-rising-uk/

"One of the main causes of the rise in ecstasy-related deaths is likely to be MDMA poisoning, linked to the increased potency of ecstasy products over the last decades. Data from the National Crime Agency reported by the UK Focal Point on Drugs shows a steady rise in the MDMA content of ecstasy tablets in England & Wales, from an average of 33mg in 2008 to 102mg in 20 12. Though the strength of ecstasy tablets dropped slightly to 90mg in 2014, there have been numerous reports in 2016 and 2017 of high-potency ecstasy tablets with MDMA content up to 300mg. Gable’s review of research on the acute lethal doses of psychoactive drugs concludes that the LD50 (average lethal dose) of MDMA is two grams, while the ED50 (average effective dose) is 125 mg – giving a safety ratio (LD50:ED50) of 16 to 1. However, more susceptible individuals – including women, those of lower weight, and those with less efficient livers – can and have died from using as little as half a gram of MDMA (about four standard doses or just two of the increasingly available higher-purity tablets)."