If you are putting 10-20k bums on seats in a 50k stadium it is fine and allows additional advertising with the giant seat cover things in unused stands. For Edinburgh it was 3k in a 67k stadia, which is just awful but you'd still get people wanting a bigger stadium with modern facilities. The Lions crowds always look awful, but if they were on track to win a tournament suddenly 55,000 fans crawl out of the woodwork. Southern Kings were similar. Two men and a dog most days then 20k when they were in with a sniff of playoffs. That sort of fluctuation is probably very strange to European fans.
Waratahs look like an excellent example of a club struggling about where to play with crowds of up to 10k. They've been hopping between the giant Allianz stadium, a more modest 10-12k capacity place and awful looking cricket or aussie rules place.
Anyway, fat lot of good the sellout did Edinburgh, who got a big, fat L.