It’s hard to say exactly without seeing the statement, since it seems each one is slightly different, but I’ve seen it where the processing fees are burdened to the NGLs, even though it’s both the gas and NGLs going through the plant. It’s just easier for accounting departments to take a fee and apply it to just one product rather than splitting it.
There also may be different places the deductions are happening that makes it not apples to apples. For example, the gas stream may have some of it’s “deductions” taken off in the form of volumes because the volume of gas sold is actually the final “settlement” volume. I’m looking at a plant statement in front of me here where the gas volume is only 94% of the actual gas processed because that’s what’s in the contract. The other 6% helps cover plant fuel and fees.
All the conditioning fees, gathering fees, transportation fees, etc have to go somewhere. I’ve typically seen it applied to one or the other, either the gas or ngl’s, not both evenly. Also, these are typically fixed fees where you pay a certain rate per volume processed. Fuel is also usually a “fixed” type fee. This would make the % fee higher in a low price environment and low % in a high price environment. (Like the % of tax added on at the gas pump. If state and federal tax adds $0.384 per gallon, this is a higher percent when gasoline is $1.20 than when gasoline is $4.00).
Is this along the lines of what you were asking?