They actually don't use HTTP, they use RTMP, try it yourself: Load up a Youtube video and scrub to the middle of the video. It will load to that very point even if it hasn't buffered that far yet.
They use HTTP with an addition in their servers similar to this plugin: http://h264.code-shop.com/trac to do HTTP scrubbing.
Google also used Akamai for its Google Live broadcast which indicated that their network couldn't do RTMP (at the time).
There's an "Akamai markup" which is a well known thing that Akamai charge for the heritage (somewhat analogous with the so-called "Mac-tax" except the Akamai "tax" is agreed to exist). A better comparison would be CDN pricing for Limelight or CDNetworks, the other two big players. It's worth bearing in mind that a lot of peering contracts for major carriers (but not necessarily Tier 1 - for example BT, Telefonica etc) depend on having a backbone - Akamai doesn't have a backbone, their backbone is the internet.
Also Google only do HTTP, so no Flash RTMP or Microsoft streaming which you effectively subsidise with an http product from a CDN.