The breakdown on costs (including total melamine used if it had to be purchased, even though I had the 5 shelves and only had to purchase the back and sides):
3/4" Melamine - 1 sheet makes 4 shelves, a 2nd sheet makes the sides and back, a 3rd sheet the extra shelf and divider for the top section - $75
1/4" Plexi sheet 72" X 36" - $60 for all 8 sliding doors
1/4" Plexi sheet 24" X 30" - $10 (to replace the door I broke)
Aluminum track for sliding doors - $130
Heat Pads: 3 large - $75
Heat Pads: 2 small - $40
Locks, screws, silicone caulking, mounting tape, cable hooks, special blades for the plexi, hole cutting blades, wood putty, vents and casters - $70 /-
Total cost - $460 (this includes total cost of melamine, which I had most of already).
Most of the materials were purchased at either Home Depot or WalMart, the exceptions being the heat pads from Bean Farm and the aluminum track from a local glass shop. Because the shop doesn't normally carry aluminum track, it was a special order and I had to pay their shipping in addition to the cost of the track. I also have enough track left over for two more cages because I had to buy the 12' lengths the manufacturer makes, not just the four sets of 4' lengths I needed. The four foot lengths are because I'm housing two adult boas in it, a juvenile albino burm, and my juvenile boas in the top two smaller sections. I doubt this will ever sag because of the way I assembled it (probably overkill on the screws, but it provides extra support as do the aluminum tracks). The precut shelves didn't come in the size I wanted, plus as mentioned I already had melamine shelves the right size, so I only had to purchase a sheet for the back and sides to use with the shelves I already had.
I didn't have to purchase the thermostat either, because I already had it for the flexwatt I was using in the cages these snakes were already in, so you can add another $130 to the total for the Helix model I have. I didn't include that in my estimate because there are other thermostats out there that cost less, but I wouldn't use any but Helix. Even adding in the thermostat (making a total of $590 now), you're still looking at a minimum of $200 per large cage and $100 per small cage ($800 total) if you're purchasing manufactured cages, and they won't include the heat or the locks for those prices in most cases (the exception being Moonstruck with their heat source and keyed locks). I could have done a few things differently and saved some money. Glass would have been cheaper than plexi, plastic tracks instead of aluminum, etcetera - but I don't feel it would have been as secure (which is a must for me) and so I spent a bit more to get what I wanted.
In regards to the litter dam, I didn't use one because, #1 I didn't want the snakes to have anything to grab on to when I was trying to remove them, and #2 I don't use loose litter, I use cotton sheets so there's no litter to contain and most of my boas consistently 'go' in the water bowls or a back corner so no problem there either. In regards to the locks, they are necessity in my book when housing large constrictors. The smaller ones probably can't move the plexi, but the larger ones could and I never intend to be on the local news for my escaped boids. 
Raven