The issue with things like this is that the most money is made with repeat business.
So are you saying that heroin dealers make most of their money off first time customers? I would bet 90%, if not more like 95%, of most dope dealers business is repeat business. And the difference between it and ex is that usually those same repeat customers come every single day. I think most people would be more prone to fuck somebody over they see once in a while then somebody they see every day, sometimes multiple times a day.
It really wouldn't pay to sell someone 100 tablets, half of which are legitimate. People who go about fucking others over, are already greedy; they wouldn't do this; they would either try to fuck you over as hard as possible, or not at all.
I don't see how you can make such a broad statement like this and act like it's a fact, how would it not pay? You're still giving someone half bunk shit, maybe it'd be better for you if you just ripped 'em for the whole 100, but remember dude wanted to test some pills so you had to make sure he had a good chance of gettin a legit one.
Most people who do this sort of thing, either go all out, or wouldn't bother doing it at all.
Again how can you make such a broad statement, do you know every drug dealer in the world? I musta met a a lot more shady people in my day then you have because it's called "luring them in" People are always sketched out at first, so you lure them in with some real shit, then burn em for as much as you can. And that can happen with any drug.
Do tell though, how many people have reported buying 100 tablets of X, only half of which were legitimate? I don't recall hearing anything along these lines. People may buy 100 bunk tablets, or 100 good tablets, but anything in the middle (a mix of good and bad), IMO, is highly unlikely.
Aw ok, I didn't realize since me or you never heard a report about it that it's never happened.

I mean come on, me, Unbreakable, and Tommyboy all said that we've never seen stamps vary that much from the reports we read on here but everyone else keeps insisting it's somehow the norm to copy peoples stamp and fill it with bullshit. Like I said before, obviously the stamp thread was pretty reliable or it never would of got to 3,000 posts. Take some time and read thru it and you consistently see people rating the same bags the same ratings give or take 1 point usually.
Another thing is with stamp names a lot of times they're specific to a certain block or hood, so not only do you need the glassines and rubber stamp, you have to take over someones block. I think it'd be easier to buy a pill press then win a turf battle.
I however, confronted the dealer every time it wasn't as good as before by a considerable amount (if I typically went through 1 gram in 4 to 5 days, and all of the sudden the newest gram I got was gone in 1 or 2 days, obviously there is a problem here, either the quality or quantity is lacking), and my dealer would make up for the difference and then some, every time.
I'm going to go out on a limb here, but I'm willin to bet you was buyin off a whiteboy in the suburbs and payin a premium. Of course dude can reimburse you when he's makin what I like to call "suburban profits", sorry if I'm wrong. The thing like I said before stamp bags are obsurdly cheap(Like as cheap as an O.E. 800 40oz, if not cheaper) when you're buying 10 bricks at a time or something, it's simply more economical to put it out how you got it and get all the repeat biz and sell the 10 bricks in 2 days then it is to dump em all out and fill em with bullshit and hope it don't take you a year to sell 10 bricks.