You can set the maximum number of workspaces that each user can create. To do so, update your Helm chart and set the CODER_MAX_WORKSPACES_PER_USER parameter to the maximum allowable number:

# Allow each user to create no more than 100 workspaces
coderd:
  extraEnvs:
    - name: CODER_MAX_WORKSPACES_PER_USER
      value: 100