Unless you boy specific VSX licences or VSX appliances, you wont have any possibility.
By default (in general), VSX appliance come with 10 VSs (VS0 / hyperviser count as 1). When you are in cluster, VS licences dont stackup. So if you have 2 members, each with 20 VS licences, you are limited at 20 VSs on the cluster.
Keep in mind virtual switches does not count.
Looking at your case, @Bence is actually right since every appliance is either sell as "standalone" appliance or "VSX" appliance for a little more where both are different SKU.