Comment by PetitPrince

I see that a insulated (triple layer) window around 100 euros [ https://www.leroymerlin.fr/produits/bauplaza-fenetre-en-pvc-... ]. Let's assume this retailer makes a 2x margin, so real cost is 50 euro.

A webcam on Aliexpress is around 5 euros. Throw in a microcontroller that's like 2 euros on aliexpress, a 10 euro screen and you still have a 30-ish euro budget for the actual door that's probably plastic (acrylic and something like PE ?). So yeah, probably more expensive.

But that doesn't means that doesn't exists ! We can see that all the time in supermarket, but I guess their needs are different.