I wanted something inexpensive for carrying my lunch and extra clothes to work and didn't want a plastic crate. Cost me about $4 in 1x2s. Already had the rest (wood glue, screws). Still need to throw a few coats of polyurethane (have that as well) on it to seal it.
Did a test ride after mounting it. The added weight is noticeable but not horrible. Overall I am pretty happy with it.