Usually, these numbers are available to members of the NMMA. www.nmma.org
But, the report is like $225 for members and $450 for non members.
Limited info is available for free:
Inboard Boats-Ski/Wakeboard Boats: 2005
Total Units Sold 11,600
Retail Value $ 435,382,800
Average Unit Cost $ 37,533
Most dealers look at the numbers in their state. For instance, the numbers for New Boat Registrations by Mfg for Illinois 1/1/05-8/31/05 only came out a month or two ago.