At all the standard fannish/literary cons in the UK we don't do comp memberships (not even for the concom). I paid my membership to be co-chair of the British National (Eastercon) in 2004. I pay my membership and am on the committee of every Redemption convention, and I'll pay my membership to be Events Manager at this August's DiscWorldCon. And for none of them do I get a refund, a discount on my hotel room, an upgrade on my hotel room or even free food. As staff/gophers some conventions will give food/drink vouchers (very rarely as much as $2 for an hour's work, more usually £2 for a three or four hour shift).

And that's at events up to 1,000 (or more).

It's a cultural thing. And I wonder whether timill may have correctly identified one of the things .... certainly I've seen the same "I'm not going to be able to do enough hours to get the free gopher t-shirt, so I'm not going to bother" happening here as well, which is possibly one of the reasons we very rarely do that.