Well, if you haven't considered the cage yet, then that's something to think about.
Bedding... A decent-sized carefresh package would cost ten bucks (and carefresh is the good stuff). You can get bedding for less, but...
Toys? Haha, as I've heard many people say, if you've got a creative mind, some cardboard (tissue boxes, toilet paper rolls), and material+thread, you're set. The store bought toys range as much as one to two dollars to fifteen or more, if you want to get elaborate, at Petsmart.
Food? Haha, I underestimated Suebee's mix. When they say it makes alot, they mean it makes alot. It cost me a bit more than the aprox. $20, but that's because I got the good stuff =) Things like Mazuri, a bag that could last awhile cost me six bucks. It should last me awhile ^w^
As long as you keep out the costs of the big things, like vet trips and the cage, it doesn't have to cost more than, about $15 a month.