After experiment with various pricing models. I have decided to go back to the old freemium + one-time purchase upgrade. The reason is that the market for Options trader is small. And the app is reaching its maturity, which means development will be slowed down. So subscription model cannot justify this. This will be implemented in the coming weeks or month. I don’t have a exact date. I believe Apple or Google will let you use the app until the end of subscription if you already have one. If not, please email me with any problems.