Villas can be super affordable when you're travelling with large groups. I'm the CTO of a startup that provides these sort of vacations. It's pretty common that the per person rate works out to much less than a hotel would be and you get the added bonus of an entire house!

Here are a couple of examples:

Sleeps 24 - $4,501/week - http://demeure.com/properties/villa-turquesa--2

Sleeps 13 - $4,569/week - http://demeure.com/properties/casa-fermentini

It was $10,000 for 16 people. 10 days. Food and private chef included. That's about it for amenities.

You can find great places on http://homeaway.com/