First of all, welcome to the forums.
Second, I have attached a workbook with two options. The first option simply removes Seller from the view and changed the aggregation of Price to Min. This gives us the minimum price within each SKU. The second option keeps Seller in the view and uses a filter-- sum(Price)=window_min(sum(Price)) -- to only show the Sellers within each SKU that have a price that matches the minimum within each SKU. This is accomplished by putting the Filter field onto the Level of Detail, right clicking it, hovering over compute using, and then selecting Pane Down (this forces it to restart for each SKU so that we see the minimum for each). Finally you just need to put this onto the filter shelf and keep the True value.
Hope this helps,
Min.zip 13.2 KB