Are you sure you need so much memory allocated to VMs? Worth mentioning is this blurb from Vagrant's old docs (http://docs-v1.vagrantup.com/v1/docs/base_boxes.html):

Make sure the default memory allocation is not too high. Most people don’t want to download a box to find it using 1 GB of RAM. We typically set it at 360 MB to start, since that is the size of most small slices.