Hi, and welcome to the forums. You will find different prices on chinchillas depending on where you live. I have noticed that states with a lot of breeders will have lower prices then states where there are only a handful of breeders. Breeders who breed for show quality tend to have higher prices then breeders who don't. I price my chinchillas at $100 standard, $150 beige, and $200 for everything else. I have purchased breeding stock for my herd where I have paid $250 for a standard because it was excellent show winning quality and considered a herd improvement animal.
It really depends on the quality of the chinchillas you are buying. Retail price would easily be $400 for the chinchillas alone if they are breeding quality, not counting the cage. Don't count a pregnancy in the price figuring. Depending on how far along she is the move could cause her to loose the baby.
Also, are you buying them to be pets or with the idea of breeding? If you want them as pets you should consider how friendly they are and if you are compatible with their personalities. Adult chinchillas are pretty much set in their ways. If you are wanting to breed you should ask how many litters she has had before, how they turned out (did they all survive), that sort of thing.