It is important to have a separate pair of cutters for cutting memory wire so you don’t damage your good flush cutters! Memory wire cutters are more heavy duty cutters which will not be damaged by the hardness of the steel.
Xuron makes a really good pair of memory wire cutters, but as long as they are specifically labeled for cutting memory wire, most other brands (like Beadalon or Beadsmith) should be just fine.
Like most tools and equipment, the less expensive memory wire shears will certainly get the job done! But if you plan to be cutting a whole lot of memory wire and doing so often, keep in mind that the cheapest tools will probably need to be replaced a little bit sooner than a higher quality pair.
If you’re just starting out working with memory wire and not sure if you’ll be sticking with it, go for a cheaper pair of shears; if you become enamored with the world of memory wire jewelry, you can always upgrade to some better cutters!