Larry,
The price varies by trailer size, and IIRC, I saw prices from about $1,000 to over $2,500 for the week. My Father-in-Law joined my sons and I, and I wanted to make it comfortable for him, so I rented a 30' trailer with AC for about $1750 for the full week. Could have housed several more than our 4 too. Site with hook-up added about $250 or so.
Many of the companies will prorate for less than the full week too.
Not the cheapest solution, but with air, and being a relatively short walk to the main gate, Sleepy Hollow and the rental trailer made it a very nice trip.
Marshall, I probably won't be in SH this year. I may do a T&G at OSH this year, but a 50th anniversary for the in-laws, a Navy Reserve retirement (mine), Raven formation flying and Pylon Racing Seminar are competing for summer/fall funds and time. Definitely want to do it again in 2012, and hang with you, Don Hall and the SH gang again!
Cheers,
Bob