The Volume discount doesn't work for group purchases, it's only meant for home cockpit builders that runs FSX on several PC networked on the same LAN.
The activation code will be only one, the activation pool is shared (since the user is supposed to be the same), and reactivations request coming from all different networks will likely be denied.
So no, you can't really use the Volume discount to share the purchase between multiple users and if you do, it might work initially, but there's the risk everybody would be then cut out from the purchase, without even the chance to ask for a refund, since the license clearly allows only ONE user.
Several machines, yes, but always a single user.