Well, it all depends where you would like to position your product- class market or mass market. Also there is an issue of short term gains versus long term gains.
May be IIMs don't feel the need to move into the mass market; may be they don't think that they will be better off, even financially if they move into mass market.
Well, let us assume that IIMs can admit some 20,000 people and get teachers who can teach all these people, then what will happen?
Will all these guys get jobs? what kind? Will they get at least a lakh more than they are getting now?
If not, what is the fee IIMs can charge?
1 lakh? 3 Lakhs? What would be the net gain after meeting all the expenses for IIMs? It could even be negative compared to today's situation- one doesn't know! I guess one will learn all this in micro-economics, marketing and finance
After all this you might sneer at IIMs for destroying the brand