ml2json parallelizes the JSON and HTML generation, meaning, all CPUs are used by default (see --cpus option) and the processing is sped up on multi-core machines. This entails the biggest part of the processing. The first phase, including mbox and MIME parsing, is not parallelized currently, and it makes up for only about 1/4 or so of the total duration, but it could still be parallelized easily.
Cost: $40
⇒ Cost range: $40