If you can, I'd check Craigslist for cages, you can get Ferret Nations and other quality cages for cheap on there, around $75 to 150 probably, then you can just alter what you get and save money. I also highly recommend making your own fleece accessories if you can, making liners, hammocks, etc. costs a fraction of the price of buying them (I lined three cages and made fleece accessories for about 30 bucks, which would only buy you a fleece liner set if you broke down and bought accessories). Then wooden ledges, toys, dust, dust containers, food, hay, water bottles, etc.
For three chinchillas I've probably spent about three hundred bucks on supplies, food, etc. (I've only had Chinchy for six months, and the girls I just got and have been replacing things), but I didn't have any initial cost for cages since they all came with them, and I just made alterations. Even if you get a chinchilla on Craigslist, you still will most likely have to throw away and/or replace most of what they come with, so they all ended up costing about the same to outfit their cage for me. (Chinchy came free from my landlord, cage and all. He's my little love bug.)