This interesting infographic (via information is beautiful) is a great way to visualize and compare certain avenues of revenue on the internet for musicians.
Although at first glance it seems a little odd to compare single song sales alongside album sales and single streams/hits the infographic is aimed at showing how many transactions of each are required for a recording artist to earn US monthly minimum wage ($1,160).
A concise explanation of the data can be read here.
The infographic does not take into account revenue via licensing or publishing royalties.
Data for Publishing royalties (paid to composers of songs) are included in a spreadsheet linked to at the bottom of the graphic.