Indeed, these are high quality subsidaries that should grow at a PAT >15%. Currently, these contribute to about 5000Cr of the 68000 Cr PAT of HDFC (about 8%).
For sure, you cant buy earnings of this quality at a PE of 20 in the open market which is what HDFC sells for now.
A light weight valuation of HDFC below. One should certainly make more than 10% going forward. Can be closer to 15% I think.