This is basically how many kickstarter campaign works. 1- capture emails, 2- tease people that they will get notice of campaign open so they can get the early bird discount (40%). 3. This causes momentum and others see it as an awesome deal and jump in; fearing they will be left out. This is how many campaigns strategize and get 30% funding in less than an hour. Use it as a psychological lure. It is basically the whole iPhone waiting in line when it comes out mentality. Use it your advantage. By capturing the emails early, you get a good feel for interest/demand to gear up for production.