Emirates holds 60,355 fans, and gate receipts are split three ways - the home team, the away team, and the FA.
Tickets are £10 in the lower tier, and £20 in the upper tier - if purchased before 12th September.
There are more upper tier seats than lower tier.
At a conservative estimate, if they sell 30,000 upper tier tickets at £20 each, and 10,000 lower tier at £10 each, that makes £700,000. Split three ways, that would make £233,333. And yes, it's only the Carling Cup, but Arsenal vs Blades matches always seem to get good attendance.
Add in the prize money for getting to this round, and it's probably not too far off. Either way, it's certainly less of a gamble than buying a player outright, I suppose. This is kind of like a 'try before you buy'. And let's not forget, this is assuming that his wages are actually £30,000 per week.