Sorry for spending too long time breeding the idea. There are many factors to integrate for a service rather than a simple commodity retailing.
For example, a Kits designer decided to build 20 kits for a start, she/he/it should provide the documentation and deposit for us to initiate the service. For 10$ basic cost plus the IC, customized manufacturing, and etc which is 2.5$. So the initial deposit is 250$. Then we list for preorder (optional), 22.5$ you say. Depends on the feedback, we will go producing and distribute the kits. As the 20 kits are sold out, we will return the deposit 250$ and profit of 22.5*20-12.5$*20=200 USD.
Attached is the draft process for your inputs: