1996 Jetta Brakes Question

I've got a 1996 Jetta GLS with discs on the front and drums on the rear
wheels. At my 72000km (about 45000 miles) - the dealer told me that I was
at 20% pad wear on the front and 30% on the back. So I asked them what the
cost was to have the brakes done on this car - almost $700.00 Canadian.
This huge price is because they won't machine the rotors, they just replace
them. The reason I was given, is that the factory rotors are made of an
inherently soft material and machining usually will take the rotor below the
minimum specification, so it isn't worth trying to turn them.

Can anybody tell me if this is in fact true?

Troy Rossmann
Sequoia Green 1996 Jetta GLS