[Malleys]

возможно так

$(document).on("keyup", function(event) {
	var jquery = $(event.target).closest("div.b_list");
	if(jquery.length === 0) return;
	
	var id       = jquery.find('.b_id')     .val();
	var quantity = jquery.find('.b_quntity').val();
	var price    = jquery.find('.b_price')  .val();

	var newPrice = quantity * price;
	console.log(newPrice);
	console.log(id);
});