Capping the price at $150/mo isn't really a wise decision. If a big customer like MLB wants to use Tapalytics for their iOS app which i assume has millions of MAUs, you will still be forced to charge them $150/month because that is your top most tier and it comes with unlimited MAUs.
In the long run, there is a good chance that a significant portion of your revenue might come from enterprise customers who would be willing to pay you multiples of the $1800 ARR. Adding an enterprise/custom quote as the top most tier is a vey common practice. Looking at the pricing page of similar companies (Kissmetrics, VWO, Optimizely, Mixpanel) might help.
In the long run, there is a good chance that a significant portion of your revenue might come from enterprise customers who would be willing to pay you multiples of the $1800 ARR. Adding an enterprise/custom quote as the top most tier is a vey common practice. Looking at the pricing page of similar companies (Kissmetrics, VWO, Optimizely, Mixpanel) might help.