I have the same problem. Paid 25$ and after 10 days the transaction is still not processed (16 sats per byte is unacceptable ...)
https://blockchain.info/tx/759303c6cf3481a5038c301b515ac44137e81105973a2e515fa24f85998b52e8

I sent a bunch of emails to support and they ignored all the messages!

In Terms of Use it says that it will be processed in maximum 24 hours! What is the next step? When it will be confirmed? I am losing money because of the delay! I am very disappointed about this and if it does not solve as soon as posible I will never use the CEX.IO!

10.4. The User acknowledges and agrees that Deposit and Withdrawal Transaction in Fiat currency may be delayed due to bank verifications and checks, for a period up to one (1) month. Similarly and due to the inherent nature of the cryptocurrency networks, the User acknowledges and agrees that depositing and withdrawing Cryptocurrencies into/from his/her Account may take between one (1) hour and twenty-four (24) hours, barring unforeseen or unavoidable network issues.