I am a engineer and toolmaker/fabricator. I also am as cheap as they come, Dutch background. I couldn't make a pair of wheels as cheap as purchasing the Cat Trax. Wife bought them for me when we got married 20 years ago. I don't use them much and they are stored inside. I never had a problem with wheel leakage. $$ per year is cheap. Like Matt said, don't sell them with the boat, especially if you plan on getting another catamaran. I always lock them to my trailer as I know they are valuable.

When something works, the people using the product will sell the product for you.