The arithmetic
A whole-house rate is charged per night, not per person, so it divides. Ten people in a four-bedroom villa are each paying a fraction of what a hotel room costs, and the larger the group the better it looks. Two couples in the same house will find it dearer than two rooms — that is the honest end of the comparison.
The other saving is the kitchen. A group that cooks two meals a day at home rather than eating out three times is often saving more on food than on beds.
What actually changes
You get the whole house: no corridors, no other guests, no fixed breakfast hour, and a garden that belongs to your party for the length of the stay. Children can be loud. Somebody can cook at midnight. The group can sit up talking without moving to a lobby.
What you give up is hotel service. Nobody makes the beds daily, there is no room service, and if you want a cook you arrange one in advance rather than lifting a phone.
Booking direct rather than through a platform
Booking sites charge a commission, and it comes out of the price one way or another. Coming direct to the owner is usually cheaper for you and better for them, and you are speaking to the person who actually has the keys — which matters when your train is late or you need a cot.
It is always worth checking the villa's own website before booking it elsewhere.