License plates up to 500 are not necessarily rare in all cantons.
In proportion to their population, several cantons still have many of these plaques. Unlike in other cantons it's exceptional to see them in individuals or companies (for example Geneva, Fribourg, Valais or Zurich).
carplates_switzerland has created various albums with plates up to 100 (for Neuchâtel, Bern, Solothurn, etc.). Here is a link for Neuchâtel = http://platesmania.com/albumlist727