Sorry but these isn't a less expensive way to amplify your X-10 signals. However, you may be able to reduce AC line noise that may be interfering with your X-10 singals, and you can also purchase more sensitive X-10 modules and switches. If you can isolate the cause of line noise, you can purchase individual noise block modules for about $25 each. If you only have a few switches and modules, you could replace them with more sensitive switches and modules and that might help (however it this method may cost almost as much as the amplified signal coupler).
As I have mentioned before, in the end it is usually less expensive and less headache if you go the amplified signal bridge. This is especially true if you are thinking of expanding your home automation system in the future.
RCI Automation[Link: ourworld.compuserve.com]