This is marketing DECEPTION at it's finest. Bigger and more yardage sounds better right? Well here is the TRUTH...
Now these people making such claims are technically RIGHT. There is no "right and wrong" about this. However, I myself (before I knew how to do tutus myself" would look at these massive amounts of yardage and just marvel. The average person who doesn't sew is going to be deceived by the yardage. For example...Lets take a look at one of my mini tutus as an example and the following ways I could describe it

I could describe the amount of tulle used in this tutu in different ways. I COULD say "oh its got 4 yards of tulle in it"
or...I could market it as 80 yards of tulle! To the average consumer, which sounds better? 4 yards of tulle at $15? or 80 yards of tulle at $15? Of course "more is better!" mentality is going to win...
LOGICALLY: how the HECK is 4 yards the same as 80 yards?
It's all in how you buy the tulle! Tulle bought on a spool is typically 25 yards LONG and 6 inches wide

Tulle bought on a BOLT is typically 40 yards long and 54 inches wide

Therefore... 25 yards of 6 inch wide tulle is a much smaller amount than 25 yards of 54 inch wide tulle.
I am NOT at all saying that it is wrong to use a bolt or use a spool. I am not favoring one for the other. They're the exact same thing. However you cannot rely on the yardage mentioned on a tutu listing as they do not specify the width of the fabric used. Bigger "sounding" is not always BETTER!