Those numbers are ridiculous. I saved up about $100k in 3 years at a tech job and I haven't worked in the last two years on that, no problem (living in a not-inexpensive US city with a car, also).
Edit: It seems the $800k includes Apple's cut. As an app developer myself, even considering that amount is torturing yourself. Apple _only_ report the remaining 70%, especially when you consider promo codes, refunds, etc... - doing a crude sales*price is somewhat inaccurate.
(Fun fact: I'm an Australian developer. Of the amount I get paid, I also need to deduct sales tax for any sales I make to Australian consumers. For a 99c app, I would make 63c for Australian sales and 70c for other countries).