Is it permissible to pay for a commodity via PayPal in installments with usurious interest, knowing that there is a dire need for the commodity and an inability to pay its full price?

Purchasing in installments via PayPal is permissible because the site is neither a seller nor a lender, and the percentage it takes is a commission for transferring the installment, which is known in advance and has no relation to the sales contract. It is stipulated that the installment contract between the buyer and the selling entity must not include an increase or penalties for late payment.