It would be grossly unusual for a single user. Grossly, extravagantly, extremely unusual.
I'd wager that less than 0.1% of all cannabis users approach 4g/day. They may binge up to 4g on their heaviest day of all time, but average far lower.
I would argue it's very unusual if only because the set of all people who can access 4oz/weed per month, and can afford the $1000-$2000/mo ($24,000/yr!) hobby is very small. Add up all of the trust fund kids with enough money, time and access and you have a tiny, tiny number of people.
An average heavy user can only afford that much weed if they're dealing and skimming, and supply and demand insists that not everyone can be a supplier. Even so, I'd wager the average heavy user chooses to use far, far, far less than 1oz every other week.