What's best re-engagement tool to build after Push Notifications?

We looked at the Push Notifications space. While the view and click rates are 10-15% times better than emails. We felt that the pricing for these tools is so high that it was restricting many website owners to use them better. So we built a push notification tool Truepush.com (while initially free, we made it paid now but the most affordable tool in the market with our current feature set. Now, we are looking to build more tools. We are toying with the idea of building something like Hellobar but at a much affordable price without losing on quality. (for example, we send 15Bn push notifications at Truepush and the product is doing good). I am wondering. Is there any other tool in the market, that you feel has better engagement rates but can be built with better pricing in mind? I am very curious to know what we can do to help more people save costs and increase engagement.