This is not a question about fluctuating exchange rates or anything, it's much simpler: Is there a bulk discount built into the Exchange mechanic?
So far I have always assumed that, even if the RATE changes, every single gem is still worth the same at any given time. Meaning that if (for example) 1 Silver can buy you 1 Gem, then 20 Silver would (at that very moment) buy you 20 gems.
However, I noticed that this is not true, and even did the math just now. Right now, to buy 1 Gem I would have to trade 1.39 Silver. That would mean that to buy 5 Gems, I would have to trade 6.95 Silver. But I don't. 6.95 Silver buys me 7 Gems instead. This means that there is some kind of bulk discount, completely unrelated to the fluctuating rate.
So the question is: Is there any research on this? Maybe a table that lists how this discount works?