The laws of the State of Washington defer the monetary value of traffic fines to the Infraction Rules for Courts of Limited Jurisdiction (more commonly known as the IRLJ), specifically
But wait, the fine listed in the IRLJ is only $42. Where did $101 come from?
In addition to the base fine in the IRLJ,
There are probably other clauses which add to the fines and penalties. I remember investigating this a few years ago and convincing myself that after taking all the fines and penalties and assessments and whatever-else-they-call-its into account, the total did come to $101. (Actually, they bring it to something close to $101, and then another rule about rounding kicks in.)
And you won't get the numbers to add up to $101 any more because there were changes to the fee schedule in July 2007. The fine for basic traffic infractions is now $124. The new calculation appears to be 42 × 2.05 + 5 + 10 + 2 + 20 = $123.10, which rounds up to $124.