Let me say a bit more.

Faxed invitation letter is allowed, but not emailed copies. Although original copy is preferred, they are not fussy about faxed copies.

The only country I knew charging an exit fee is New Zealand, China has never asked an exit fee in the history.

The paper work confusion started 2 weeks ago. Majority of athletes attending the Olympic Game does not require a visa to China, they only need a special permit, which when depart from China, like leaving USA, and they need to hand that remaining paper back to Chinese immigration. Guess what happened, a lot of "very intelligent" sports personnel packed that paper into their check in luggage. That caused a big trouble for themselves and Chinese authority.

As long as you are not an athlete attending the Olympic Game, you don't have to worry additional paperwork when leaving China, just fill in a departure card.

PS. I have attended a lot of long meetings in China, still can't believe you have a "week long meeting"