Did mine for RM800 inclusive of theory & pool sessions, equipment rental plus, the instructor came to my place at my convenience. Open water sessions separately charged... cos that one is subject to so many things like accomodation, where you choose to do your open water etc. I chose tenggol, cost me total of RM600++.

Hence, Open Water Course - RM800
Tenggol - 600++
Here you will get your license so total spend (cheapest) is RM1400

I bought my equipment (at discount price), except for regulator and BCD, total was RM1200.

So my initial cost is RM2800. You can choose not to buy equipment but its better than renting.