Ask HN: Conversion rate of a "commercial" landing page

Hello, I'm looking into online advertising at the moment. My project is based on a Yearly subscription model. 15$ / year to be exact. I've done some advertising for a free service where you only required to input your username, email and Password with no email validation and my conversion rate was around 25%. With an appropriate landing page with some A/B testing what kind of conversion rate should I expect for a commercial "product"? Cheers,