I think that the main problem is probably that most people, although interested, want to see that it will perform and be reliable before sending their money. I for one am very interested, but a number of factors are holding me back, like exactly how much will the gain be, how much will the installation cost, how reliable will it be, will I be able to get it to Canada without paying some crazy duty, etc. I'm sure if you had a working prototype you'd have 3 times the people signing up and sending in a deposit. Unfortunately you need the deposit before you can make a prototype, and that creates a vicious cycle...
