why the earning of same offer changes

i see in the list of my offers that there are many offers with the same web but different in earning
example
ebay
diino.....
i hope admin can clear this

It depends on the budget for the advertiser to target a specific country.

For example : eBay pays for the US or UK sign up more than the others like Italy , Philippines,etc..
Just because the advertisers want to target his products mostly for those countries :-)

Correct.