Pak obviously does not have forex to pay, but Pak may be paying off using some other means. Contract of Saindak Copper-Gold project with MCC which also owns ~52% stakes in it. So far MCC has earned ~$2 billion, actual amount difficult to ascertain due to both Pak-China gov/mil policies.
Project has been extended.
Pak and China close allies, Pak provides a 2nd front engagement to India on behalf of China, it is by default also, but it serves massively to PRC strategic interests.
May advantages Pak provides are intangible, like recent J10CE, PL15E advertisement not just for sales but also a deterrent vis a vis Taiwan, the whole multi domain war theater.
Same relationships Pak had with USA with FMS/FMF, though it was transactional.