I have configured the following:
Red Membership - free - lifetime subscription, default on registration, not prorated
Orange Membership - $2500 merchandise - non exclusive, multi plans can exist, only upgrade, prorated
Orange option - $5/mnth - exclusive required with orange
Yellow Membership - $5000 merchandise - non exclusive, multi plans can exist, only upgrade, prorated
Yellow option - $5/mnth - exclusive required with yellow
...
I have tried this using just all subscription plans and a combo of subscriptions & merchandise as above.
When I go to upgrade from Red to Orange, I get a plan cost of $2 plus the $5 subscription for an initial amount owing of $7 and recurring payment of $5. If I try and upgrade from Red to Yellow, the Plan cost is $5 ... ?
I have Promotions enabled (they require a coupon code), but even disabled, there is no change in the plan cost.
I have multi-currency enabled and switching between CAD and USD changes the subscription component price, but only the C currency designation changes on the Plan purchase price, the amount does not.
Using the latest Joomla release and the latest CBSubs package.