Inspections are free, if your boat is found to be contaminated they will clean it free.
I do believe the seal goes from the boat to trailer somehow. The seal is good until it is broken - like when you launch your boat.
You will also need a Lake George Park Commission Boat Registration Sticker.
"All Vessels 18 Feet or Longer, or Any Vessel Mechanically Propelled by a Motor 10 h.p. or Greater, Must Register with the Lake George Park Commission and Display a Registration Decal.
Boats may be registered annually or for one day or week."
This will cost you by the foot.
Private marinas will charge you around $50 to launch.