How to buy support/update only when I already have the plugin?

I don't understand your pricing structure for support/update once the plugin has already been purchased. I purchased the plugin on March 9 with six months of support for $34. So my support/update subscription expired on September 9. I want to renew the support/updates. our four levels of Plugin Prices all include "get the plugin." But I don't need to get the plugin again. I already get it back in March and installed it. What's your deal - every time a person wants to renew the support they still have to pay the full "get the plugin" price all over again?