F Visa Formalities

(F) for business:
Original and copy of Invitation Letter issued by authorized government organization like the local foreign affairs office. But always we have pay USD200-USD250 to the party who arrange same for us. Say If I ask my supplier/agent, they ask processing fee. It's troublesome and expensive. How to avoid this hassle ? My new supplier only sent me an Invitation in their Letter Head. Is that enough for get Chinese Visa ?