The Rife Frequency Generator and Royal Rife, the parent company, exists not only to sell you machines but to disparage other modes of treatment, such as chemo and surgery for cancer. (You can understand the agenda -- you wouldn't want someone to deteriorate on your machine and then be monitored clinically, or later helped by other options -- not a likely source of a happy testimonial.)
As a health outcomes researcher who worked at a leading cancer center for six years and sadly knew some of my colleagues as patients as well, I can tell you with confidence that chemo and surgery actually do slow down and in some cases cure cancer. Period. Ripping patients off is one thing; persuading them not to treat disease conventionally can amount to shortening their lives.
Admittedly, modern medicine doesn't offer anything for ALS from the "cure" standpoint, but there's no point in wasting hope and dollars on a machine that was a fad in the 1930s, when we knew far less about the causes of disease. Clearly killing "microbes" isn't going to fix a disease that isn't caused by them. Nor are there any controlled studies demonstrating that a Rife machine has ever killed any pathogens at all, let alone improved health status by any objective measure.
Money can buy a lot of things that might make life better for someone with ALS. A Rife machine isn't one of those things.