It wasn't a clearly made point then! As a rough guess, if it does not include the costs of borrowings, the costs (i.e. including repairs, routine refurbishment, empty rates and management etc) might more typically be around 15% for a mixed portfolio.
The ROI can tend to be a bit misleading in any event. The income return should be based on the current value - not the historic costs of acquisition or investment. If CRT manages to keep the income stable and secure a substantial increase in capital value, the % return will appear to fall. But if CRT experiences a reduction in capital value (not good news, surely) the % return increases.