but when a company is sitting on cash equal to +20% of their value
It is a great point that 20% of thier value was cash. However, I discount that amount because I don't trust companies stockpiling cash. If you can't put it back in the ground, just start paying a dividend.
I think it's difficult to see the price being much lower as their earnings continue to rise.
That last assumption is VERY dangerous. MARGIN COMPRESSION will be the pitfall for AAPL's valuation as soon as they go 4 or 5 years without completely changing the landscape of the technological world.