AWS: Elastic Bean Stalk, VPC and multiple sites

I am looking to set up multiple sites with AWS using Elastic BeanStalk I currently have 2 different sites setup each in there own VPC each with there own NAT and RDS instance and R53 Hosted Zones.

I want to spin up more sites however if I follow this model it will start to get a bit pricey due to the extra NAT's and RDS's.

Is it a good idea to have 1 more VPC set up and set up separate Elastic BeanStalk ENV's for each site and then just bump the NAT and RDS size and have a new hosted zone for each site that points to a particular ENV?

Thoughts?