Only $3 and takes all of five minutes. Completely solderless to boot.
For a smaller bristlebot kit thats great for adults and kids, visit BrownDogGadgets.com. You'll have a little bristlebot running aound your place in no time.
Step 1: What You Need
Dollar Store Items
$1. A Cheap Electric Toothbrush. We're stealing it's motor.
$1. A cheap scrub brush. Try to get one with little to no rubber grips on it.
$1. AA Battery Holder. With attached leads.
$0.50 A little switch. Optional really.
Around the house
Copper Wire. Steal from other stuff if you can, you only need a tiny bit.
Hot (melt) Glue Gun
Wire Strippers (Optional)