[{"brand_id":"A","price":500},{"brand_id":"A","price":700},{"brand_id":"B","price":1500},{"brand_id":"C","price":100},{"brand_id":"D","price":400},{"brand_id":"D","price":600},{"brand_id":"D","price":200}]

db.collection.aggregate([{$setWindowFields:{partitionBy:"$brand_id",sortBy:{},output:{total_sales_by_brand:{$sum:"$price"}}}},{$match:{total_sales_by_brand:{$gt:1000}}},{$unset:"total_sales_by_brand"}])