What are the specific instructions for placing a PCB+Assembly order? The pricing is always the same regardless of the board size or number of components.

Hello, I found a few different projects from your site that I would be interested in purchasing - the boards along with the assembly. I'm a little confused though about the entire process. Every project I have viewed is the exact same price - regardless of the number of components that are to be assembled. If I want to purchase 20 boards with assembly of less than 10 components, your site shows a price of $30. But if I want to purchase 20 boards with assembly of several dozen components, the price displayed is also $30. It doesn't really make sense to me that the pricing doesn't change when purchasing larger boards with several dozen components compared to purchasing a small board with only a few components. Am I doing something wrong? Can you refer me to a page which shows the specific steps needed to place an order? Thanks.