Using primitives can be error prone and hard to understand in large argument lists, since it difficult to determine the identity of a value. Named parameters are helpful but really all values should use a domain type.
Scala provides value classes to implement domain types without incurring the associated runtime costs. In particular, it avoids the need to allocate an instance on the heap.
The documentation (AFAIK) does not cover the serialization costs.
The following code defines a simple domain concept, using four different designs.
Samples are then serialized, using Java Serialization and Kryo; with the number of bytes listed in the table below.
The numbers indicate that value classes have no impact.