The amount you earn from streaming and downloads varies between platforms.
Payments from downloads are either from a fixed wholesale price which is not directly connected with the retail price, or you will be paid a fixed percentage of the retail price less a payment to the publisher outside of the US, as well as any applicable government taxes.
Streaming works differently. Either a streaming service receives income from advertising or customer subscriptions. Those income streams are then divided each month based on the total numbers of streams from all rights holders on the platform. In a similar way to downloads, deductions for publishers and government taxes are made prior to payment to you.
For more information on platform specific royalty payouts please refer to their respective website(s).