Unless you actually need one of these machines, I guess I would pass on them. Cabinets -- unless they are extraordinary -- are not worth much, plus if the existing machine head doesn't work it's tricky to find another head that will fit the cabinet without modifications.
A rotary machine in a cabinet usually weighs a *ton*. This is not an ensemble you want to move into your home unless you are sure it works and are sure you are going to use it.
Is the $25 machine a portable? Portables sell more easily than machines in cabinets just because they are ...well... portable -- easier to move around and taking up less space if stored. If it's a portable it might make a good backup machine, but even then I'd want to bring some thread and fabric to the store to make sure it actually sews and forms a stitch.