Except your premise is wrong, same mistake as the OP. You are assuming difficulty will increase by something like 30% perpetually, which simply is false and impossible. The increase in difficulty will also slow down exponentially. We will probably NEVER see a 30% increase again. We are seeing mostly 20% increases nowadays, and soon even 20% will be history. So your "expert mode" calculator will also paint the wrong picture for you, because it assumes difficulty increase perpetually, which is simply UNTRUE, we've had many many difficulty DECREASES in the history of Bitcoin. We will probably see this phenomenon again within 6 months or so (as long as the price stays at $500 level).
I agree that it is impossible for the difficulty to increase 30% each period forever. HOWEVER, it doesn't have to do it forever, it only has to maintain that rate for a few months to have almost the same result.
For example, a miner that currently mines 1 BTC per 2016 blocks will mine about
4.3 BTC total if the difficulty increases 30% each period forever. On the other hand, if the difficulty increases 30% each period for 6 months and then 7% after that forever, the miner will mine about
4.4 BTC. The second case is much more realistic, but it has nearly the same result.
I think you missed the part where I said we will probably never see a 30% increase again, last six diff changes:
Feb 28 2014 3,815,723,799 21.92% 27,314,015 GH/s
Feb 17 2014 3,129,573,175 19.39% 22,402,357 GH/s
Feb 05 2014 2,621,404,453 19.49% 18,764,744 GH/s
Jan 24 2014 2,193,847,870 22.59% 15,704,175 GH/s
Jan 13 2014 1,789,546,951 26.16% 12,810,076 GH/s
Jan 02 2014 1,418,481,395 20.12% 10,153,885 GH/s