In a poor year like this year I agree with the 20,000 additional. Though the Roos game on the Friday night in round 7 probably would've pushed 55,000 this year in all likelihood..True.
Essendon play 8 games this year at the G ( 4 home and 4 away ) and 9 at Docklands.
They are effectively evenly split between the two grounds with both home and away games against the bigger Victorian teams almost always at the G.
Docklands does impact but it is easy to overstate it. Their 7 home Docklands games consist largely of inter state opposition plus the likes of the Dogs, Saints and Norf and in a year like this I suspect playing 9 games at the G instead of 4 - which would entail transferring 5 of those relatively unattractive fixtures - would be good for about 4,000 per game extra with an aggregate increase in attendance of about 20,000 overall.
I suspect that Melbourne this week would have drawn about 33 to 34,000 to the Dome with 4,000 extra at the G and this would be true of most "non marquee" match ups. 4K by 5 extra games= 20,000.
In the stronger years on field, this difference would likely be significantly larger. A top 4 Essendon playing most Vic clubs would likely draw between 50-75,000 at the G. Agree with yesterday's fixture being at Ethihad 33-34k. However given a fine day even yesterday would have probably drawn 45,000. That's a 11-12K difference between the crowds pertaining to the venue on this day. This is because Essendon and Melbourne have large MCC followings that don't go to Ethihad.
In years when a strong Essendon would play equally strong Vic clubs at Ethihad (eg games V Hawks and Cats in recent years) we have sadly seen in many instances 10-30,000 locked out per game. Therefore, in strong years on field this variance could be upwards of 80-100,000 in a year.