Magic, broken calculator or just a "divorce"?

Those who remember the 90s are well aware of the game in thimbles. The leader has three identical thimbles, under one of which he hides a small ball, after which he quickly rolls the ball between the thimbles or changes the thimbles in places. Then the player is asked to guess under which of the thimbles is the ball. The deception is built on the so-called imaginary passaging, in which we are shown one thing (it seems that the object being manipulated has passed from hand to hand), and in fact do another (and in reality the ball is not where it seems to us).



Do you think the time of palming and passaging is over? Not! Magic is next to us!
Everything said further is not a complaint and that it should not be such (according to the habr rules), there will be no quoting of correspondence with technical support, only facts, figures and screenshots.
Also, perhaps, the article is not quite in the format of the habr, but I think that most of its users use electronic exchangers, therefore - let's go.
Further many images.

It took me just now to buy the NNth cryptocurrency amount. I knew exactly the amount I needed, so, as usual, having monitored courses on changeinfo.ru, I chose an exchanger that I use for several years. In general, the acceptable courses were in the first 4, and all of them we will see:
')


Algorithm with all the same. On the first page in the window desired to purchase the amount, enter 0.04 BTC and click on receive / buy.

exchanger1.com
Enter the amount:



Click "change":



Magic deftly "ate" 25% of the amount.

obmenka24.com

Enter the amount:



Change:



Enter the amount
obmenka.me



We get:



And my favorite is smartwm.biz (aka smartwm.ru )

Enter 0.04:



And we get to the exchange all the same 0.03:



Well, agree, do you often check the amount at each stage of payment? Or calculating it on the first page just automatically click on the rest?

Investigating further it turned out that the magic is not only going on when you click on the "change" button. I will give an example only on the last exchanger:



I.e:
purchase rate: 30706 for 1 BTC
for 1228 rubles we are offered to buy 0.03 BTC
While 30706 * 0.03 = 921.18

Magic again "ate" 300 rubles.

Maybe it's just a display glitch?
We make a payment in one of the exchangers and we actually get less than we were shown at the first stage.

Maybe this is a glitch of calculations? Ask for technical support exchanger. Can they return the difference, say “thank you” for the bug found?
I am not quoting, but the essence of the answer “everything is correct, it is listed as much as they promised.

I appeal to the monitoring system of exchangers, but the appeal quickly disappears from public viewing.

I would like to believe that this is just an accident and several exchangers “broke down” at once. But when exchangers “break down” at the stage of calculating amounts, i.e. it is the wrong functionality that a priori is essential for them to work, unkind thoughts creep in - gamblers again have you raped.