Thanks everyone.
redchaser- That is a good question, one that I have been thinking about recently. If I was to buy a 375 gallon tank from glasscages with a starphire glass front and overflows, the total would be about $2100. Right now, I have spent about $1150-$1200 on glass, silicone, and overflow setup/sump. The glass alone was about $850 (but that does include the starphire upgrade). So there is some significant savings there. I also get to customize the tank exactly how I want it (my overflow will take up much less space in the tank than the glasscages overflows).
If I had just wanted a barebones tank, with regular glass, and no overflows, I probably could have built that for around $750. If you can find used plate glass for cheap, that will help reduce costs. You can use the used glass for the bottom, the back, or have it cut up for use as bracing. I picked up a piece of 1/2" glass 5'x3' for something like $10 and took it to a glass shop, and they cut it into strips for my eurobracing. They charged me $50 to cut it, but it still probably saved me about $100.
Unfortunately, that isn't going to be the total for my project, as materials for my stand and bracing my floor (which I have yet to do) aren't included in that figure. I'm not factoring in the price of the suction cups, as I would have bought those anyway to help move the tank had I bought one preassembled.