How much should a spark plug replacement and tune up cost?

The one issue I really have a problem with here is this so-called “transverse engine” charge.

JMHO, but that is a way of squeezing you a bit on the labor by insinuating that a transverse mounted engine is more difficult to access than a linear mounted one. They vary, and a real flat rate labor time takes the “transverse” part of this into consideration.