What Wulf said. Before you spend money on a new seat, go talk to your local auto upholstery shops. Discuss not only lowering, but any discomfort/hot spots you have with the current seat. If they quote you a high price, move on to another shop. Some shops do this when they aren't interested in taking the job on. For reference, you will spend $400-800 for a true custom seat from one of the motorcycle custom seat makers like Russell Cycle Products, Rich's, Terry, Laam, etc.
If you want links to custom seat makers, let me know. Since you haven't put your location, (city, state), in your profile, I can't suggest some close to you. Knowing your location gives context to your questions and allows others to give you better answers.