As others said, depends on many factors.
At only a small discrepancy, I probably wouldn't say anything provided its good and I otherwise have a good relationship with the dealer. Also you gotta keep in mind, unless you know someone who can get it 100% pure, it's never a real gram, it's a gram of a street drug being sold as heroin. So long as it contains diacetylmorphine, at a high enough purity for me to consider the price reasonable, I won't make a fuss about it. So long as it remains consistent.
What's important isn't exact sizes, what's important is that it be consistent, either as good or better the significant majority of the time as it has always been for that price, barring shortages beyond our control. So long as I know how much money or weight get me how high, consistently once taking tolerance into consideration, and conformed by other users of the same dealer. And that the price is fair for that, then it's all good far as I'm concerned. It's only a problem when the same amount of money clearly gets you less of clearly the same batch as it used to without being told in advance of purchase. Or if the same weight is significantly less good than it used to be but the price unchanged and again wasn't told in advance. Taking increased tolerance into consideration as a possibility too of course.
It's not complicated, I want to know I got what I paid for, and that how much I paid for what I got was fair. However you go about it, if this criteria are met, all good. If that however is not the case, and I wasn't made aware of that before purchase despite the dealer having to have known, then I've been ripped off. The more trust and respect for the dealer I have the more ill give them the benefit of the doubt.
Now if I've been ripped off, it depends. I'm a girl, although I do know one girl dealer, and her stuff is consistent and good, it is however a little bit pricy. A little, not a lot. If she ripped me off, which to my knowledge she never has, then I might call her on it, see what she has to say. Worst case scenario, she loses a customer.
All other dealers or sources I have are men, and I wouldn't even begin to be able to match their strength if violence broke out. So I either let it go and they lose me as a customer (the luxury of having several sources). But if it's REALLY bad, like they've ripped me off big time and did it because they felt I had no way to retaliate. Absolute worst case scenario. I might inform some of my stronger, more experienced male friends from my social circle, and see what they think about it. If they think the guy ripped me off big time andor took advantage of me. Well I don't have to say anything, they'll likely want to do what they'd do if it had happened to them.
Like I said it all depends, every situations a little different. And usually id rather take a small loss than risk someone getting hurt. But very rarely theres an exception, like a new friendly source or dealer, who turns out to be not so friendly after I remind them they asked for payment in cash, not 'service'. Or more likely intentionally implied one price to begin with, then another after, and when that's both too expensive and wasn't the agreement, "generously" offer another way to pay back my supposed debt because they "feel bad that I misunderstood how much they were asking". Situations like that, which are thankfully rare for me since I'm fortunate enough these days to have several good connections that can be trusted, and have good products for fair prices. (Only been pressured for sexual favors or sex once in quite a long time now) Some still pull bullshit, but it's the fairly benign "be there in 5 minutes" arriving an hour and 20 minutes later bullshit. I can put up with that. One has it all just about, fair price, good and consistent H, fast (whole things done from call to sale in 10-20 min usually), and friendly, personable, and never hit on me. And for that he's rewarded with a reliable trustworthy regular customer.
