My setup costed me less than $10. Here is a list of what I used.
4- 3mm blue LED's = $2.00 (lsdiodes.com)
2"x3" project box = $2.29 (RadioShack cat#270-1801)
Powersupply = free (came with MS Sidewinder Forcefeedback Joystick, most 5vdc or 12vdc powersupplies can be found for ~$5)...