[Kaveren]

This is true, but in practice there's a good chance they will be released if you pay. I don't have statistics on this on hand, but from cursory knowledge I'd be surprised if it was less than 70%-80% of the time a ransom was paid, the person would be freed. Statistics on that sort of thing are hard anyway because many kidnappings go unreported.

Ethics aside, killing the person after you receive your ransom simply worsens your punishment for little gain (provided the hostage can't identify you). Besides, should you want to take future hostages, it lowers the likelihood of being paid.