This is typically an occurrence, and there is no need to worry so much when this happens. A locksmith will be able to help you get back into the car in no time. However, you should bear in mind that having your keys locked in the trunk doesn't necessarily mean that you are locked out of your car. At times your car doors may be open, and if this is the incident, then you can gain access to the trunk and get your keys.
It is essential to be mindful that some car trunks might be much harder to get into than others. This will probably influence the price but not in any drastic way. It is also crucial to check if your trunk is deadlocked or not. Deadlocks offer an extra layer of protection on some vehicles, but they also make the unlocking process much harder for a locksmith.