CNC cutting or die cutting?
Flat rubber parts are made in two main ways: with a cutting die (a steel rule shaped like the part, pressed through the sheet) or with a CNC cutting table that follows the drawing. Each has its place.
CNC cutting: no tool at all
The machine reads your file and cuts it: there is no die to make or pay for, a change of design is just a new file, and a first part can be cut as soon as the material is there. It is the natural choice for prototypes, spares, small and medium series and large parts.
Die cutting: for very large runs of small parts
A die costs money and time to make, and has to be remade when the design changes. Once made, it stamps parts very quickly, so it pays off on large, repeated runs of small parts.
How to decide
If the design may still change, the quantity is moderate or the part is large: CNC. If the part is small, the design is frozen and the volumes are very high: ask for both prices. The calculator gives the CNC price in seconds, which is a good first reference.