what are you talking about, what risk?!!
the network does not care about how much you are transferring. it only cares about the size of your transaction in bytes. you can transfer a tiny amount of money or millions of dollars with the same size of transaction and pay the same amount of fee.
and the fee they paid was a high priority fee which makes the transaction high priority and mineable in the next block.
additionally anybody who knows the basics of bitcoin (meaning they have read the first page of bitcoin.org/start-here) knows well enough that they need to wait for confirmation. and when a transaction is confirmed you can not double spend it anymore specially when it has the recommended number of confirmation.