It's interesting that you once (correctly) said that the 2017 preliminary crowd was extraordinary in general. Now you're saying the equivalent game on the weekend 'should be able to get at least 85k-90k' - so that's very close to the 2017 prelim crowd.
This is despite 2017 being Richmond's first home prelim for decades and Saturday night being Collingwood's seventh since 2002. By your own comments: either the 2017 crowd wasn't actually that extraordinary (because in less unusual circumstances you expect it to be almost replicated just 2 years later), or it was only extraordinary that Richmond got such a large crowd.
To be fair though, Richmond have drawn, what is, 90k plus to their last 8 finals? That in itself is unprecedented.
So in effect they were the first club to drive the 90k trend for Melbourne based finals