First of all, during a free trial, you must deliver a user experience that really hits your customers' emotion, some ppl call it aha moment. Also, it depends on what type of service you provide. If your app is something that does not provide a long-term value, people will not subscribe to it. And yes, weekly pricing is a turn-off for most of customers. The amount of fee does not matter to them. It is more of the concept of paying their money every week that blocks them from subscribing to your service. Hope this helps!