[{_id:1,data:[{price:"2",title:"title-1"}]},{_id:2,data:[{price:"2.0",title:"title-2"}]},{_id:3,data:[{price:"2.00",title:"title-3"},{price:"2.99",title:"title-4"}]}]

db.collection.aggregate([{$project:{data:{$map:{input:"$data",in:{$mergeObjects:["$$this",{price:{$toDouble:"$$this.price"}}]}}}}},{$match:{"data.price":2}}])