I built my refugium out of a 10 gallon tank ($9 at Wallmart), 5 custom cut glass panes ($5 at Ace Hardware), Aquarium Silicone ($2 or $3), substrate (?), HF Pump ($95), PVC plumbing ($30), overflow box ($50 at Ebay), and 2 daylight compact fluorescent bulbs (5,500K, 26 Watts Each, $7 each at Home Depot)
Total of about $180 or $190.
It has done the trick with the Nitrates. I have two types of Macro growing in the refugium along with some live rock.
I also built my skimmer for about $50 or so.
Skimmer design 101
http://www.hawkfish.org/snailman/skimmer101.htm
A good list of DIY plans
http://www.hawkfish.org/snailman/snailmandiy.htm
If you decide to do any DIY stuff feel free to hit me with any quaetions as I have traveled the road.
I also did a real cool float switch to prevent overflowing the main tank if siphon is lost in over flow.
Bruce