Not an attempt to hijack the OP's thread, and I certainly don't work for them.
But if you're looking for the best price for NGK plugs look no further than RockAuto, I have been buying plugs in bulk from them for years and have literally saved thousands
Not sure if you guys in the US save a great deal, but for us guys in OZ it's well worth it.
I also buy my O2 sensors from them.