You can pay considerably less than $5000.
For anything less than 53 feet, you can pay close to scrap value.
I recommend reefer trailers.
You will pay far less w/o the reefer unit.
Containers are far more secure and heavier.
You'll need a chassis or arrangements for moving.
Insulated containers have been rare where I am.
Far more secure than a trailer.
I can make a number of suggestions for locks and lock upgrades.
I am currently changing to the A2500 locks.
I have used the 6325 and 6327 on standard trailer keepers.
There are many higher end options.
A proper kingpin lock may be called for, as well.
The best ones are expensive, but fairly foolproof.
Tracker devices are now an option.
There is a wider offset hasp for doors with raised gaskets.
Container doors present special issues, but there is a clever solution.
There is also a remote lock with interior lock points.