We will be adding support for networks with multiple gateways after resolving the high-priority stability issues that are being tracked in the following thread.
That includes a fix for the "Xenons cannot always reconnect to the Cloud after a gateway update / reset" which is the leading cause for Xenons that are stuck in a flashing green state.
One additional note is that the pricing you referenced is only applicable for customers who participated in the preorder pricing and have contacted support for grandfathered pricing. The link you referenced is an artifact from the preorder campaign that has been updated.
All pricing for new customers is current at Pricing | Particle