Just wanted to give anyone heading to the show in Hanover that most of the mid priced (€150-200) hotels in downtown are already booked, and the airfares from the U.S. to FRA are running above $1600RT. If going book ASAP
A trade fair in Hanover is not causing the prices of airfare to Frankfurt to increase.
Your quote about 1600$ round trip is not valid because it depends on where you are flying from in the US, the date, and most importantly, the airline.
If you are having problems finding cheaper airfare, go to Kayak. If you need cheaper rooms, try the tourist info in Hanover as they may have blocks of rooms set aside.