1. Streaming is basically a perpetual source of revenue. If 1 download is equivalent to 200 streams then ask yourself how many times on average does someone listen to a purchased song?
2. The comparison you should be making isn't to digital music purchasing but to radio royalties. The formulae for this are complicated (flat fees to BMI, ASCAP, etc and then a complex formula after that for distribution to writers but currently not performers, except for Internet "radio").
Of course streaming (renting) earns you less than a purchase.
The recording industry likes to paint this as the artists are getting screwed. And they are getting screwed but not by streaming services. They're getting screwed by the recording industry [1].
Fact is, very few artists can survive on CD sales and digital downloads alone. Most artists survive by performing and even that's being eroded by the recording industry who uses fall guys like Ticketmaster to charge "fees" that fall outside of the revenue split with the artist on ticket sales. The public hates Ticketmaster. Artists hate Ticketmaster. The industry loves Ticketmaster.
[1]: http://www.techdirt.com/articles/20100712/23482610186.shtml