Having owned many motorcycles over the years, I have always thought that motorcycle owners, like Slingshot owners paying way too much for accessories. I was always amused that you could buy an American Tourister or Samsonite hard side luggage for hundreds of dollars less than a top box for a bike.
The luggage pieces are much better made than than a Hondaline piece. I got tired of paying gold prices for tin parts, and always tried to find something that would serve at the purpose for far less. "Waterproof" form fitting luggage $600?!?!?!? Pack your stuff in a plastic garbage bag, stuff it into a cheap canvas duffel. $25. Chances are, the duffel bag will be thicker and have better zippers than the form fitting ones.
It's like buying Army Surplus or Prada.