My data on the Saxon regiments taken into Prussian service in 1756 comes from Jany, Vol II, page 375; the names of the Prussian Chefs seem (at first glance) not to coincide with those you have listed.
What is your source for the statement that Prussian fusilier regiments were somehow cheaper, 2nd class troops than musketier regiments? Were they numerically weaker? Did they get paid less?