Supernodes will constantly be influx as the price goes up/down, and like the above said, earns around ~400 XEM per supernode.
Converting that to dollars or fiat depends on the current price of XEM and price of BTC.

However, the program states:
https://forum.nem.io/t/nem-supernode-rewards-program/1735

"The payout started at 70,000 XEM per day and will be split among all nodes that pass the tests for the day.
This payout is planned to be increased at regular increments"

Fun vote here:
https://twitter.com/xemcoin/status/755088825404260356