Why are paypal partner fee so high on Swappa

[IamAbundant]

Hi. 

I just sold my old phone on swappa and got charges 2.9% fee + 17% partner fee. No where does it say that partner fees are 17%. Can someone please explain that to me please. Here's the transaction fee breakdown.

Tax                    $10.21

Purchase total   $126.21

Fee                    -$3.96

Partner fee       -$20.21

Total                 $102.04