There are several cheaper drives but none that offer the value for the money spent. Most other stepper drives use off the shelf stepper driver chips that offer only a fraction of the performance of the G250 drives inside the G540. Then if you add in all the ancillaries to get the same feature set: optical isolation, two high current relay drivers, VFD output, charge pump circuit you will spend almost as much money and get lower performance. I have a lot of customers who started with the cheaper boards and when they finally moved up to a G540 (because the cheaper board was not satisfactory or blew up) they are shocked by the performance difference.