Yes I a gree that Roland's prices for the SM cards are overly ridiculous. $35-$60!!!
I think that the MMU that deals with the SM cards has an upper limit - Maybe 4MB. What this may mean is that you may only be able to store a limited number of patches on a SM card, not matter how large the memory capacity is.
I know that my SP-202 can only take up to 4MB. I've heard failed tries of larger capacities. What you need to do is take the chance and see what happens.
The Infamous EPU.