Am I reading right? 7g a day?! Roughly $80-100 a day on weed?! Thats insane. Your tolerance is not at all surprising. From my experience, the quality of weed in Sydney can be both ends of the scale. As far as quality is concerned, its usually pretty good, the quantity is sometimes less than average though.
My advice is to give up on trying to find different weed, and take a break. If, for some unfortunate reason, taking a break isn't on your cards, I'd recommend finding a source for naturally grown weed. Good natural bush weed is easily as strong as good hydroponic stuff, the high is superior (its like 'smoothed at the edges'... more stoned than droned) and because its naturally grown there are less chemicals used in the growth and the difference really shows.
Even if you smoke different sorts of weed, I doubt you'll be easily able to reach that original level of high unless you take a considerable break or cut down. I know plenty of people who have smoked weed for a long time, and those who've claimed to have smoke natural, definately display far less of the 'stoneresque' values. If you're not going to stop smoking, then at least try natural stuff for a while, in the end, it might be slightly beneficial.