You also have to take into consideration the fact that United have had more event games over the last 30 years than Wendy have. They had never been to the new Wembley, and not been at all since 1993 before their play off v Hull. They were also full of beans for that game as they thought it was a shoe in the arrogant bastards. On the other hand Unitedites had been treated to nothing but serial failure on the big occasions. It naturally turns people off from attending those games if in your heart of hearts, you expect to see your club fail.
I've never really got the massive attendances at Wendy thing either. I think it's mainly a myth. Yes they have had some good attendances in the past, nearly 40k v Man Utd in the early 90s and a 48k attendance against the same side in the mid 80s...coincidentaly when Man Utd would have brought thousands and thousands to those games and probably had many in home areas also. How many times could we actually say they have had way more than 30k home fans in attendance for those big gates? Probably not a lot if truth be told. Yet Utd are now averaging over 30k without nearly as many away fans as the Lepers Lane has historically hosted, and if the Lane was bigger this season I'd suggest that we would be averaging 35k plus this season.
Considering the bigger size of the rust bucket over the Lane over many decades, the slightly bigger historical average attendance that they have over us is pretty marginal/pathetic, especially when you consider that they have seemingly always been seen as the glamour club of Sheffield with stadium improvement handouts etc, and they will have enjoyed many a huge away following bulking up their figures.
Wendies huge potential attendances are just a myth. There's a reason why they are so insecure about attendances compared to Blades.