Nope, read again. Its $4.99 and to quote:
Now for the catch...the glow plug comes attached to our #8901 COX SureStart Production Engine...meaning you get the glow plug, standard cylinder, piston, piston rod, crankcase, crankshaft, drive washer, snapstarter spring, plastic "SureStart" back plate and needle valve for less than half the price of a new standard glow plug. All of these parts are included, so don't wait, quantities are limited and this offer won't last forever.
So that $5.99 shipped with glow plug and engine. Good deal! I already have one of those engines. I am working on the construction of the Nitro Hairdryer as soon as possible.