[{"price":123,"totalPrices":[{"totPrice":123}]},{"price":12,"totalPrices":[{"totPrice":123}]},{"price":143,"totalPrices":[{"totPrice":143},{"totPrice":123}]}]

db.collection.aggregate([{$match:{$expr:{$eq:[{$size:"$totalPrices"},1]}}},{$unwind:"$totalPrices"},{$match:{$expr:{$ne:["$price","$totalPrices.totPrice"]}}}])