Assuming it does matter, in which direction does the value flow?
Here's the complex part. The value is not expressed in bits and it depends on the destination within the peer's network. I am assuming that we can map the IPv4 address space by city and that we can set some value to each intercity link. This means that a stream of bits entering a peers network in San Jose with a final destination in San Jose would be free. But if the stream of bits was destined for Santa Cruz there would be a small cost. And if it was destined for Sacramento there would be a somewhat larger cost because Sacramento is further.
Ok, here comes the Bell System all over again. This would have the effect of trickling down to the point that you would be charged more for downloading a web page from Germany or ftping an encryption program from Australia than you would for getting a web browser from Illinois. Start looking for peak/off-peak rates, different long distance billing, etc. Sounds like a good way to regress.