This is not a fair representation of the project feature. I'll reproduce the original announcement for reference:
We are pleased to announce that you can now use Earth Engine with
Google Cloud projects! What this means is that it's now easy to set
up a collaborative workspace where you control permission to read and
write assets from a central asset storage location (learn more). You
can use your own Google Cloud projects to track your Earth Engine
requests, assets and permissions. You can also track the success rate
of requests you are sending to the Earth Engine service, to help with
debugging and optimization of your Earth Engine powered workflows.
All this comes with a new, opt-in Code Editor experience that lets you
see and organize assets stored under your personal Cloud project or
any other project to which you have access. You can still list and
manage Earth Engine assets in a Cloud project from the Earth Engine
command line, Python API or REST API (learn more). We've also
provided documentation to explain how to get set up and running with
the new Cloud integration.
For all those interested in opting in to the new system, click the
button in the upper right of the Code Editor to create a new Cloud
project or choose an existing one to use with Earth Engine.
As we previously announced, Google Earth Engine is building on Google
Cloud Platform capabilities to enable new workflows and unlock
exciting new advancements in machine learning and artificial
There is no charge associated with creating a Cloud project. For over
a decade, Earth Engine has been a free, powerful tool for academic,
research, and non-commercial users, and we're excited to add these
features to allow you to do even more.
Specifically, you do NOT need to pay for computations and you do NOT need to pay for storage. (The exception is for companies or organizations who have a commercial contract with Google, in which case charges to an individual account should not happen.) I suspect that you incurred charges from using some other Cloud feature (such as AI Platform or Cloud Storage).
In terms of benefits, sharing of assets is not only easier, the asset path of project assets will not contain your username, but the name of the project instead.