It's the sales strategy by the club. They incrementally release the tickets as and when they are required to create the illusion of scarcity.
You predicted around 5k though didn't you?To be fair, higher than I predicted. Absolute credit to Brighton fans that we can get that many at those prices.
I don't think the WSU tickets were ever put online and the policy was to see expencive seats 1st and ones that would show on TV.
I bought the £28.00 in the WSU wing but was able to move to the many spare seats in the centre.