So you say Germans claimed 77,000 aircrafts on the Eastern Front while actually shooting only 20,000.
Seems probable.
Recently some historians evaluate the real number of Hartmann's victories as around 90 (or 80 - 120, precisely).
Here is a thread about this (the fact that many of his victories don't find confirmation in Russian sources):
http://forum.axishistory.com/viewtopic. ... 84&start=0
What is also suspicious about his victories is that he claimed a relatively very small number of bombers & Sturmoviks compared to fighters. While on average 50% of Russian planes that flew over the Eastern Front were bombers & Sturmoviks, fighters were a much smaller percent. Here is also an interesting discussion about that (in Polish):
http://www.dws.org.pl/viewtopic.php?p=1450710#p1450710
They posted some interesting info on numbers of German aces (according to Nazi Germany's data from WW2):
More than 300 air victories - 2 (Hartmann and Barkhorn)
Between 200 and 275 - 14
Between 100 and 199 - 92
Between 60 and 99 - 128
Between 40 and 59 - 232
Between 5 and 39 - over 2532
In total Germany claimed to have more than 3000 aces in WW2 (ace = at least 5 air victories).
Out of the total of 236 aces who scored (were granted) over 60 victories, 133 were Killed In Action or captured (Eastern Front - 87; Western Front - 46).
Among the Soviet pilots according to the same link only 15 (!!?) aces scored (were granted) more than 40 victories. And the best of them (as well as the best of all Allied pilots in WW2) scored 62 / 64...
It seems that it has something to do with German overclaiming...
Because Germans also lost thousands of aircrafts on the Eastern Front (and Western Front too) - after all.
The good point is that out of those 15 best Soviet aces, only one was Killed In Action (all the rest survived the war).
Here another data on Soviet aces:
http://www.wio.ru/aces/ace2.htm