Shipping should be less than $10, even less when combined with other kit / parts.
The Reflector mount kit is designed to not only hold the reflector in place but also give a place to mount the 4 bay kit and attach the whole assembly to the mast.
The Kit includes (2) mounting / U-clamp brackets which should be enough to support up to a 40" by 40" reflector and attach the complete antenna to a mast.

How this kit works
 
The 4 bay back bone is inserted into the socket or peg mount and screen reflector is trapped between the 4 bay socket/peg mount and reflector support, the U-clamp holds the whole assembly to your mast.  
More screws can be used to secure the reflector to the reflector support as needed, (8) self tapping screws and washers are supplied.

The socket or peg mount can be used to attach the PVC back bone frame to the reflector. The peg mount (Right) fits tightly into a 1/2" PVC fitting and comes in a choice of 2 lengths. Length 1 will give 4" reflector spacing and length 2 will give 5 1/2" spacing but can be cut down to give smaller spacing's. The socket mount (left) can have a piece of 1/2" PVC inserted in the socket and used as the spacer between the back bone frame and reflector mount this could be handy for the DIY'er who wants to experiment with different reflector spacing's.