Only started my Amazon business in mid-April and was lucky to find BuyBot Pro (BBP) pretty quickly. Thank goodness! The tool is a must-have for any serious seller. Providing real time information about products, position, estimated sales, the competition and overall ROI.
Can't recommend enough. It's an essential for me and has helped to plan for pricing and overall product strategy. Also, by comparison to other similar (but not as good) tools on the market the subscription is very cost effective.
The team who manage BBP do so very diligently and any queries are promptly dealt with. They are also very pro-active in developing a community where like-minded sellers can 'chew the fat'. Find them on facebook.