5 grams isn't a high dose though, I'm not sure why it's described as such. Shops sell doses starting at 15g, although they recommend newbies take only half of that.
Example of a shop which describes 5g as a "light dose": https://www.sirius.nl/atlantis/
You must be talking wet weight. 5g of dry mushrooms is about 50mg of psilocybin, which has been referred to as a "heroic dose" for decades.