3 pieces, 18" each for $2.85 + $3.95 shipping.
Works out to $1.51/ foot. If you buy three sets (shipping still $3.95), it works out to 92.6¢/foot and you have some around.
As for the Crayon cluster...you are planning on putting 18mm motors in which size crayon? The big one would be really cool. You could fit a lot of motors in that sucker.
I have a couple 18", a few cut between 7" and 9" and a whole bunch of MMT sized pieces (2.75"? 3"?) from kits I put 24mm mount in instead. Tell me what you want and your address. Any/all, no charge. There's a good chance such fragile things will get munged in the upcoming move, so they might as well go to a good cause.