It depends on what options you chose (like cage size and what type of bird)
My original cage cost $130 and suited the 2 birds well. The cage i brought, which is much bigger was $380
Jade was $110 cos he is a handraised bird, but parent raised birds can be quite cheap (like around $30 i think)
I brought lots of toys, to switch around all the time, which was possibly $100
Feeding them is really cheap (seeds, nuts, greens, pellets).
I would only recommend 1 bird if you're at home all day and can let the bird out most of the day. I tried having just Jade, but had to get Amber a few months later, for Jade's sake.