You need to think in detail about what is happening to understand how better design helps. If it was simple erosion at the point of first contact there probably wouldn't be much difference between simple (cheap) designs and the better ones. But when a contact bounces it generates a spark and crater in one or both contacts. Metal from the crater is deposited nearby, possibly along with non-conductive ash from lubricants or other contaminants like flux and flux cleaner. So the next time around there is more surface roughness and more electrical bounce. The electrical bounce is a combination of contact opening from physical bounce of the contact and opening due to non-conductive material between the contacts. Splitting the contact into multiple subcontacts (sometimes called fingers) reduces the probability of all elements being opened at the same time. Often the length of each finger is made different so that they have different bounce frequencies, further reducing the chances of all fingers being off at once.
There are elements of quality control in the equation also. To my knowledge no one has a complete theory of contact design allowing design based on that theory. Good companies do have thousands of hours of empirical data on the best combinations of contact geometry, spring pressure, contact metallurgy and other factors that result in good performance. Lesser suppliers usually have a design that either based on a copy of an existing design, probably without understanding tolerances and required material properties, or have a design that has limited test background and possibly wide variation in product. In some cases they may know how to do it right, but have been forced to jettison design and process elements to achieve a price goal.