3.5grams of dried subs is a huge dose. If they 'cracker dry' that can be around 30 mushrooms.
That said, I've had (properly dried) subs, where I find 1 dry gram is the rough equiv of 100ug of LSD and and 3.5grams sends me straight to god. Yes - this same batch of dried powder, I had a mate with some insane natural tollerance, I gave him around 3 grams to start with, after an hour he said he was hardly feeling it, so I gave him another 10grams, which he promptly ate all of and yeah, he said he was pretty high, but he was totally coherent and intelligible the entire night and by no means having some spiritual experience or some shit like that.
So I guess, everyone really does react different.
That said - it can also be that the mushrooms didn't dry well, if they're overly bruised, or heat is used in the drying process, I've found it can greatly reduce potency.. Also, different batches / patches of mushrooms can vary greatly in potency too.