NSE's Rs 22,569-crore IPO has opened for subscription, putting India's largest stock exchange in direct comparison with global listed exchanges such as Nasdaq, CME Group, Intercontinental Exchange, LSEG, HKEX and SGX. India's largest exchange is coming to the market at a rich valuation. At the upper price band of Rs 1,785, the exchange is valued at about Rs 4.42 lakh crore, or nearly $46 billion.