I agree with Gekke Ted. It takes a lot of time, effort and shipping costs to put custom sets together. What to think about instructions for instance, a lot of work to put them together. The result is high prices. I created some custom sets to sell on BrickLink or at events, next to my layout. Up till now, I sold some of them, especially at the events. And once in a while I sell one on BrickLink. The most important thing is that your design has to be something someone else wants to pay for.