BTW even at $275 if the sofer could write 5 mehudar mezuzos a week (most can't)
Large mezuzos? I would presume those are a little easier than small ones.
But definitely, Mezuzos are probably extremely challenging, and I can imagine why sofrim would rather write Sifrei Torah or Megillos.
Top of the line A"R tefillin are probably around $2,500 per pair (just for the parshios. A friend told me he recently ordered DIRECTLY from one of the most sought after sofrim).