"Harmful" implies "haram" - what tradeoffs exist?

In [this question](https://islam.stackexchange.com/q/38727/17702) the following hadith was referenced: > There should be neither harming (darar) nor reciprocating harm (dirar). [An-Nawawi](https://sunnah.com/nawawi40/32) This is referred to in fatawa about [forbidding smoking due to harm](https://islamqa.info/en/10922) , some [related to dangerous sports](https://islamqa.info/en/3895) , a [fatwa forbidding using the computer if it harms your eyes](https://islamqa.info/en/108657) , and numerous other issues. This brings up the question what tradeoffs exist, and how "bringing harm" is established. Obviously there are things that will clearly be classified as harmful, such as slitting your wrists, and things that will be harmless, such as eating a normal piece of bread. Some things will be in a grey area though. Riding your car is relatively safe and brings obvious benefits, but there are numerous deaths in car accidents. Free-climbing is comparatively dangerous, but lots of fun for many people - however "having fun" may not be a valid goal in sharia to offset the danger. Various sports have health benefits in some regards but can also be detrimental to one's health in other regards. Some behaviors are very weakly correlated with certain health detriments, for example certain eating habits lead to a very small increase in incidence rates for diseases, while other behaviors are more strongly correlated with harmful effects, such as smoking leading to a very marked increase in certain cancers and other diseases. These considerations bring up the questions: - "how strongly" does a behavior have to be correlated with harmful effects to become haram? I suppose in the end that's a matter a faqih has to weigh up to his own discretion, but are there any guidelines? - Do positive effects of an otherwise harmful behavior offset the harm to make the act halal? For example coal mining used to be and to an extent still is very dangerous, but there were great benefits for society to be had.