Zerodha is one of the most transparent brokers I have seen till now. They do mention the payment gateway charges. Dhan, Zerodha, and Groww offer zero brokerage on equity delivery. For intraday/F&O, it's typically ₹20 per executed order.

Zerodha has ₹300/year as a Demat AMC (Annual Maintenance Charge). Dhan and Groww don't have any Demat AMC. Account opening/maintenance fees differ for different platforms. Yes, there are some taxes like STT, GST, and stamp duty, which depend on the transaction.