Merchlytics by Merch Informer is a must have tool in your Merch by Amazon toolbox!
Merchlytics was designed to display historical t-shirt data over time directly on the Amazon page. This will allow you to see price trends and BSR trends without leaving Amazon as long as you have a Merch Informer Account.
With Merchlytics, you will have the ability to judge how well a shirt is doing in a particular niche, understand how best sellers have changed their pricing strategy over time, and how this has affected the sellers rank on Amazon.