I will try to shed some light on it. One thing that plays a role in it is that Mysore is a slow pupper for me, I got three pups in two years compared with about fifteen since then from another edible type. Another example is that right now the big tissue culture company has over 5,000 Dwarf Cavendish and only 72 Mysore in stock. As you can see, to answer your question, yes, they are harder to come by
Lastly, I really dont know of other folks that ship corms, most of the sellers on the web and even the local garden centers that aren't on the web have tissue cultures from the same supplier. Getting a pup cut from a mother plant may shave a year or two of waiting for fruit.
Anyway, maybe next year if I dont sell this one I will have more of them from when this one pups, and it will allow me bring the price down.