Oxbow is good chinchilla food ... you may want to check with your vet ... sometimes they will carry the Oxbow chinchilla food or will keep it in stock for you. $16.00 for 5 pounds is a bit much.
You might want to check some of the big rancher's websites, often they will ship out chinchilla food. The Shoots, the Ryersons, Jags ... check on the Empress Chinchilla and MCBA websites for ranchers and or breeders that also provide chin food. Traditions and Mazuri are also good chinchilla pellets. You could buy a 25 pound bag for what you are paying (or close to it) for 5 pounds. If the food is kept in a dry cool place, it can last for a good 3+ months.
Mazuri can be found in some pet stores and some Walmart stores ... check your local stores and see if they can order it for you.
You need to find a good supplier you can count on and make sure you always have plenty of back up on hand ...
Jo Ann