Right now you receive a sales report via email in the form of a spreadsheet once you are paid your royalties which works fine. Epic is most likely working on a sales tracking control panel but there is no info in regards to this as of now as far as i know.
A sales tracking system doesn’t really serve any purpose other than consolidating data and relieving the workload of Epic’s accounting department. Knowing how many items you’re selling will not help you sell more items and since you can’t links directly to the marketplace right now you can’t run marketing campaigns or use the data in any way that will be beneficial to you so i don’t see it as a necessity at the moment.
Once bundles, discounts, etc. are implemented then it would make more sense to have a control panel from which to manage all of this.
The Marketplace has only been up for about 2 months so I’m sure it will be improved considerably over the next few.