I happen to have an annual pass to WDW that is only valid on weekdays and visit about once per month. There are always numerous conventions that last between Tuesday/Wednesday and Thursday. Attendees are definitely less price sensitive (about airfare) than the vacation market. Furthermore, I've met consultants there from places like Phoenix and Denver that need to be in Orlando between Monday and Thursday every week (common phenomenon). Conversely, I've never met anyone who lives in Orlando and does the reverse.