How does international postage work on mail?

Lets say I send a package to England and it costs me 10 us dollars, does all 10 US dollars go to the US postal service? or does the money get split up between the US and British postal service? Because obviously they have to deliver it on thier end. And another question, lets say I pay for priority international, is the country I am sending my package to going to deliver it priority as well, or is it just priority to that country? and is there a formal agreement that handles these issues?How does international postage work on mail?
Some carriers handle mail all of the way, like UPS in many cases. Others, like the USPS (a national entity, not international), subcontract out and pay a per piece price to complete the delivery or they pay the per piece price to the country's in-house mail system (like the USPS) to complete the delivery. This cost is part of the overall cost paid by you at the onset.Since they all reciprocate, it often washes out pretty good.

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