[{"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([{$group:{_id:"$brand_id",total_sales:{$sum:"$price"},records:{$push:"$$ROOT"}}},{$match:{total_sales:{$gt:1000}}},{$unwind:"$records"},{$replaceWith:"$records"}])