Some wall-people sleeping right now, who knows.

The arbitrage traders will fix that price-difference very fast. One can buy @502 Satoshi, then transfer them to the other exchange and dump in the wall for @642 Satoshi.

These days we see several same cases. When Bitcoin Cash was introduced there where 100 - 200 USD price difference from one exchange to the other. As soon the deposit/withdrawal where possible the arbitrage guys fixed the price in only some hours, and since all prices are about the same over the exchanges...

jus saying it.