Unable to use Resouce value with $

I'm trying to implement a custom resources class by implementing setProperties(Properties) as outlined in the documentation:

https://tomee.apache.org/application-resources.html

The resource is defined tomee.xml:

<Resource id="myresource" class-name="com.exmaple.MyResource">
myproperty=$omething
</Resource>

But as soon as the value starts with a dollar sign, its value is interpreted as null while passed into setProperties().
My current theory is that property substitution is interfering here, but I have no clue how to avoid it.

My failed attempts include:

myproperty=\$omething
myproperty=$$omething
myproperty=\u0024omething
myproperty=&#x0024;domething
myproperty=${xxx:-$omething}