Hmm.

I'm seeing Shimano DH-2N30-E 6V 2.4W dynamo hubs on ebay for $35 (free shipping), and Foxeye StVZO 40 Lux dynamo headlamps on ebay for $13 (free shipping).

$35 + $13 = $48. Dynamo hub energized headlamp system.

You'd still need spokes and a rim - but a bike needs those anyway.

Hmm.

(Understand, this is not a recommendation. I haven't used this set up and don't know anyone who has. I was looking for other things and surprisingly stumbled across this. I had been under the impression that a hub generator & StVZO headlamp combination would begin at 2.5X our $50 limit on this thread.)