It matters only in terms of final price vs. their calculated value of the contract. In other words, all they do is look at how much you're paying vs. how much you're getting. Moving numbers around has no effect.
Example: You buy 100 points @ $100/point and there are $2000 in dues for current UY. If you negotiate the price to $80/point and pay the dues, that's the exact same thing as paying $100/point and the seller covering dues. Mathematically, it's 80*100+2000 = $10,000 for the first option, and 100*100+0 = $10,000 for the second. Same result. It's a meaningless, psychological difference only.