My advice would be: Do NOT open chests for an unusual courier.
Select the courier you want, find somoeone that have it and try to trade with him for keys, games or something else. Save money in the end.
quick question. So I wasn't so unlucky currently with the diretide chests. And im wondering, how often do unboxed couriers come out as unusual? Is there no unusual baby roshes yet? Because I unboxed 3 regular ones
Even though each individual opening doesn't affect the next, the set of openings together DO have a different percentage than a single chest. Some of you are misrepresenting the Gambler's Fallacy (also known as the Law of Averages).
To make it simple, let's say you have a 10% chance of getting an unusual with the opening of each chest. Common sense tells us that opening two chests doubles this percentage, and in this case common sense is not far off. Surely it's clear to you guys that someone opening 100 chests has a far greater chance to get an unusual than does someone opening 1 chest. Does this mean that, after opening 99 chests without getting an unusual, the next chest has a high chance of containing an unusual? No (and that's why someone correctly pointed out that your chances decrease with each failure).
To see why this is the case, consider 10 coin tosses. If the tosser gets 9 tails in a row, the next toss is still 50% likely to be tails. This is because TTTTTTTTTT has the same probability of coming up as TTTTTTTTTH, in any set of 10 tosses. And both of course have the same probability as HTHTHTHTHT (when the flips are considered in order). But still, when starting from the beginning, flipping all tails is very unlikely; you'll almost never see it. That's why considering a set of tosses changes the percentages compared to considering a single toss.
For fun, here are the chances to get an unusual courier after opening up to 10 boxes (assuming these unusuals drop 10% of the time, which they do not). These are rounded to 2 digits of precision:
1 box: 10%
2 boxes: 19%
3 boxes: 27%
4 boxes: 34%
5 boxes: 41%
6 boxes: 47%
7 boxes: 52%
8 boxes: 57%
9 boxes: 61%
10 boxes:65%
Others in the thread have explained the math behind this. But as you can see, the more boxes you're opening, the better and better your chances become of finding an unusual. Even though the true percentage per box is probably like 2%, this trend still holds true.