I have NA-M's on my car but they are Dust Free. So I cannot comment what the cheaper ones will be like. We have not had any compliants about the cheaper ones being dusty.
The Dust-Free models use the M compound which are for mainly street use where you want lower noise levels but retain the performance as much as possible. It helps to keep the wheels clean too.
"Part of the Non-Steel Series, Endless uses a Non-Steel Developmental Process with a new, mild ceramic material to increase rotor friendliness. With no steel materials, dust is minimal and rusting is prevented"
Taken from Endless USA
I hope this helps