I picked up a CHEAP Bionicle Manas set from a Dick Smith store (electronics store here in Australia) for
around $37 (AUS) - equates to about $30 US...

They aren't as responsive or as powerful as hoped, but I think will perform well in other models (this
truck is a bit heavy and runs a little slow).

They're also a bit tricky to build into a studless model... The studless links are offset and you
need to do some tricky half-stud offsetting to get them to fit.

At least the provide a challenge!