I suppose that's the disadvantage of having the tickets so cheap. Disappointing though.
You do realise the stadium holds 54,000 don't you? So if there was 40,000 as they expected there would still be 14,000 empty spaces. It's very hard to judge the attendance I'd say 30,000+ but possibly short of the top figure expected. Still a good turnout in freezing weather and difficult travelling conditions.