This is probably old news, but it has been something I've noticed.
Earlier today I took a look at the ol' dil exchange. Funny enough, while people have been hoarding dil for the upcoming s7 requirements, the price of zen has gone up, ever so slightly. It has generally been sitting at 158 for best price, but earlier it was 159, as seen here. It would seem that 159 would be the lowest price, all lower prices being bought up already. If one were to buy zen at any of those prices, one would get their zen almost immediately - which makes sense, as there's a big pool there. And if one were to pick another price, lower than the lowest shown, it would take some time until it traded, when someone put up their zen for your lower offer. This would make sense.
Except, that doesn't seem to be the case. Well, the waiting is true. But it looks like, if one were to sell their zen for dil, the best prices would be a bit different. As we can see, there's lots of zen being sold at lower amounts than the Buy Zen tab shows.
So, seeing as how there looked to be a bit of zen being offered for 154 dil a pop, a tad better than the 159 shown in the Buy Zen screen, I decided to take one lucky person up on that. While one would expect to immediately receive from such a bounteous pot of zen, I didn't. Not only that, but hours later I am still waiting for my 1Z.
I have heard some folks on this very forum suggest that Cryptic is artificially keeping a high price in dil for zen, so folks will buy zen for the purpose of obtaining dil. Now, I certainly don't believe in such conspiracy theories, but there is a discrepancy here. What is the reason for this? Is it just a bug?