I am not a doctor or pharmacologist, but I am in narc., and dealt with an in custody death due to cocaine OD many years ago––-pure guess on my part, as there are a lot of variables, especially since I don't know if we are talking inhalation/injection/oral ingestion here, but if ingestion, given that I have no clue what was in the deceased's stomach to affect absorption rates, I'd guess (seriously, this is merely a guess here,) that the person ate around 2-3 grams of retail level product.
ETA: Just to note, we don't deal with much meth around here, as a proportion of total drug use, but what we do deal with is pretty pure.
ETA 2: Wow. Just really saw the deceased's stats......we're talking someone with no more than 5 liters of blood of board, period, and nearly a 10th of a gram of pure meth in her system......wow.
ETA 3: Slight math fail on my part––-nearly a 100th of a gram in her system, not a 10th. Still amazing, but not totally out of my mind like I thought I was. I was thinking she had to have eaten darn near a quarter key for a minute there.