chelsea season tickets

I was amazed to find out to today that chelsea have only got 20-23k season ticket holders, which is at the very most only 5k more than us.
When you think of chelsea's recent success i find this amazing!
Is it because they've given over a bigger part of their ground to corporate?

I know a few Chelsea fans and they do just seem like they have a large proportion of fans who are city business men who just can't attend enough games to be season ticket holders. Might be wrong. Their ground isn't that big either considering they're a top four team.

Is it the costs involved of a season ticket there ?

That's shocking!!! So they have on average 17,000 tickets for every home game going on general sale!!! At still manage to sell out

I dunno if cost has much to do with it as chelsea's catchment would be generally more affluent than say spurs or arsenal yet they have huge waiting lists.
I dunno if they do sell out every game, even against barca last week i noticed from one of the camera angles that there were loads of empty seats in the top corner behind the goal (and this was on the opposite end to the away fans)