Have you wondered WHY they are so much cheaper? Speedmaster - currently Speedmaster79 - are off shore copies of real speed parts. Their quality not what it should be. This board - and pretty much every automotive board - is filled with threads about speedmaster failures. People fall for the low price deal every time, despite all the evidence to the contrary.
Never buy cheap parts. They're too expensive.
Spend the money once and buy quality parts the first time. You'll be time and money ahead.
SPEEDMASTER79 : COLORADOSPEED - LATE MODEL DOMESTIC (AMERICAN MUSCLE) | IMPORT (EUROPEAN | SPORT COMPACT) AUTOMOTIVE PERFORMANCE PARTS